Currently the top level directory contains basically all of the code
for the crypto package. This PR moves the crypto code into submodules
in a similar manner to what `golang/x/crypto` does. This improves code
organization.

Ref discussion: https://github.com/tendermint/tendermint/pull/1966

Closes #1956

This commit switches all usage of math/rand to cmn's rand. The only
exceptions are within the random file itself, the tools package, and the
crypto package. In tools you don't want it to lock between the go-routines.
The crypto package doesn't use it so the crypto package have no other
dependencies within tendermint/tendermint for easier portability.

Crypto/rand usage is unadjusted.

Closes #1343

This reverts commit d02c5d1e30.

Refs #1740

also, expose limit option for number concurrent streams for gRPC
(unlimited by default)

This reverts commit 96a3502

See https://github.com/tendermint/tmlibs/issues/45

comment out failing consensus tests for now

rewrite rpc httpclient to use new pubsub package

import pubsub as tmpubsub, query as tmquery

make event IDs constants
EventKey -> EventTypeKey

rename EventsPubsub to PubSub

mempool does not use pubsub

rename eventsSub to pubsub

new subscribe API

fix channel size issues and consensus tests bugs

refactor rpc client

add missing discardFromChan method

add mutex

rename pubsub to eventBus

remove IsRunning from WSRPCConnection interface (not needed)

add a comment in broadcastNewRoundStepsAndVotes

rename registerEventCallbacks to broadcastNewRoundStepsAndVotes

See https://dave.cheney.net/2014/03/19/channel-axioms

stop eventBuses after reactor tests

remove unnecessary Unsubscribe

return subscribe helper function

move discardFromChan to where it is used

subscribe now returns an err

this gives us ability to refuse to subscribe if pubsub is at its max
capacity.

use context for control overflow

cache queries

handle err when subscribing in replay_test

rename testClientID to testSubscriber

extract var

set channel buffer capacity to 1 in replay_file

fix byzantine_test

unsubscribe from single event, not all events

refactor httpclient to return events to appropriate channels

return failing testReplayCrashBeforeWriteVote test

fix TestValidatorSetChanges

refactor code a bit

fix testReplayCrashBeforeWriteVote

add comment

fix TestValidatorSetChanges

fixes from Bucky's review

update comment [ci skip]

test TxEventBuffer

update changelog

fix TestValidatorSetChanges (2nd attempt)

only do wg.Done when no errors

benchmark event bus

create pubsub server inside NewEventBus

only expose config params (later if needed)

set buffer capacity to 0 so we are not testing cache

new tx event format: key = "Tx" plus a tag {"tx.hash": XYZ}

This should allow to subscribe to all transactions! or a specific one
using a query: "tm.events.type = Tx and tx.hash = '013ABF99434...'"

use TimeoutCommit instead of afterPublishEventNewBlockTimeout

TimeoutCommit is the time a node waits after committing a block, before
it goes into the next height. So it will finish everything from the last
block, but then wait a bit. The idea is this gives it time to hear more
votes from other validators, to strengthen the commit it includes in the
next block. But it also gives it time to hear about new transactions.

waitForBlockWithUpdatedVals

rewrite WAL crash tests

Task:
test that we can recover from any WAL crash.

Solution:
the old tests were relying on event hub being run in the same thread (we
were injecting the private validator's last signature).

when considering a rewrite, we considered two possible solutions: write
a "fuzzy" testing system where WAL is crashing upon receiving a new
message, or inject failures and trigger them in tests using something
like https://github.com/coreos/gofail.

remove sleep

no cs.Lock around wal.Save

test different cases (empty block, non-empty block, ...)

comments

add comments

test 4 cases: empty block, non-empty block, non-empty block with smaller part size, many blocks

fixes as per Bucky's last review

reset subscriptions on UnsubscribeAll

use a simple counter to track message for which we panicked

also, set a smaller part size for all test cases

otherwise, we're not testing ping/pongs.
see https://github.com/tendermint/tendermint/pull/687#issuecomment-332494735

server:
- always has read & write timeouts
- ping handler never blocks the reader (see A)
- sends regular pings to check up on a client

A:
at some point server write buffer can become full, so in order not to
block reads from a client (see
https://github.com/gorilla/websocket/issues/97), server may skip some
pongs. As a result, client may disconnect. But you either have to do
that or block the reader. There is no third way.

client:
- optional read & write timeouts
- optional ping/pong to measure latency

What's new:
- auto reconnect
- ping/pong
- colored tests

Error:
```
Expected nil, but got: encoding/hex: invalid byte: U+0078 'x'
```

echo means we're returning the input, which is exactly what this
function does.

Error from tendermint:

```
panic: Expected map but got type string [recovered]
        panic: Expected map but got type string

goroutine 82 [running]:
testing.tRunner.func1(0xc420464000)
        /usr/local/go/src/testing/testing.go:622 +0x29d
panic(0xa1fda0, 0xc4201eecd0)
        /usr/local/go/src/runtime/panic.go:489 +0x2cf
github.com/tendermint/tendermint/rpc/test.waitForEvent(0xc420464000, 0xc420064000, 0xae6fae, 0x8, 0xae6f01, 0xc2e998, 0xc2e9a0)
        /home/vagrant/go/src/github.com/tendermint/tendermint/rpc/test/helpers.go:179 +0x53a
github.com/tendermint/tendermint/rpc/test.TestWSNewBlock(0xc420464000)
        /home/vagrant/go/src/github.com/tendermint/tendermint/rpc/test/client_test.go:190 +0x12e
testing.tRunner(0xc420464000, 0xc2e9a8)
        /usr/local/go/src/testing/testing.go:657 +0x96
created by testing.(*T).Run
        /usr/local/go/src/testing/testing.go:697 +0x2ca
```

More changes:

- remove Client interface (reason: empty)
- introduce HTTPClient interface, which can be used for both ClientURI
  and ClientJSONRPC clients (so our users don't have to create their own) (Refs #8)
- rename integration tests script to `integration_test.sh`
- do not update deps on `get_deps`

Use 0x-prefixed hex strings in client

server: Decode hex string args

Encode all string args as 0x<hex> without trying to encode as JSON

Added tests for special string arguments

Fix server handling quoted string args

Added string arg handling test cases to bash test script