Refs #1134

Validation:

- ignored in block.ValidateBasic since it's stateful information
- checked in blockExec.ValidateBlock

ValidatorSet change delayed by 1 block, and lite refactor (#2)

* p2p/pex: Allow configured seed nodes to be offline

Previously you couldn't startup tendermint if a seed node was offline.
This now allows you to startup tendermint, as long as all seed node addresses
are formatted correctly. In the event that all seed nodes are down,
and the address book is empty, then it crashes with an informative error msg.
(This case doesn't occur if no seeds were specified)

Closes #1716

* (Squash this) Address melekes' comments

* (squash this) fix package imports

* (squash this) fix pex_reactor comment

* (squash this) add a test case

[ADR] Proposal for encoding symmetric cryptography

[ADR] Fix malleability problems in Secp256k1 signatures

update genproto

consensus: non-responsive to CTRL-C if consensus state panics

1) no need to stop the ticker in createTestGroup() method
2) now there is a symmetry - we start the ticker in OnStart(), we stop it
in OnStop()

Refs #2072

Refs #2072

We most probably shouldn't be running any further when there is some
unexpected panic. Some unknown error happened, and so we don't know if
that will result in the validator signing an invalid thing. It might be
worthwhile to explore a mechanism for manual resuming via some console
or secure RPC system, but for now, halting the chain upon unexpected
consensus bugs sounds like the better option.

revert "make `/status` RPC endpoint resistant to consensus halt"

Closes #1944

also, remove excessive log message

Refs #2072

Closes #2072

NOTE: from the ticker#Stop documentation:

```
Stop does not close the channel, to prevent a read from the channel
succeeding incorrectly.
https://golang.org/src/time/tick.go?s=1318:1341#L35
```

Refs #2072

These test vectors are needed for comparison with the Rust implementation.
To implement this effectively, a "RandBool" method was added to cmn.Rand.

This is to reduce wait times when initially connecting. This still runs checks
such as whether you still want additional peers.

A test case has been created, which fails if this change is not included.

Our Tempfile was just a wrapper on ioutil that panicked instead of error.

Our Tempdir was a less safe variant of ioutil's Tempdir.

This uses the stdlib's method of creating a tempfile in our write
file atomimc method, with a few modifications. We use a 64 bit number
rather than 32 bit, and therefore a corresponding LCG. This is to
reduce collision probability. (Note we currently used 32 bytes previously,
so this is likely a concern)

We handle reseeding the LCG in such a way that multiple threads are
even less likely to reuse the same seed.

Refs #1712

* change validators to last_commit_info in RequestBeginBlock
* do not send pubkeys with RequestBeginBlock

Refs #1856

This commit makes it such that circle CI only shows the module whose
tests it is currently running in the log, unless a test fails. For each
failing test, it will display the name of all failing tests, along with
their log output. This is done to make
our log output far more scrollable. We lose no information in debugging.

The paper is such a useful resource to anyone building on Tendermint. It should be linked in the ReadMe.

Previously we logged `Testing for i <i>` for all i in [0,100).
This was unnecessary. This changes it to just log the value for i on
error messages, to reduce the unnecessary verbosity in log files.

* Removed unnecessary onStart & onStop calls in reactor

* Refactor OnStart & OnStop in reactor

* Removed redundant OnStart func in reactor

Refs #1772

Reasons:
- this was a bad patch for something not well understood

Lessons learned:
- nobody should be modifying code without understanding the problem
first. it will only result in more technical debt and code rot.
- we never hide information when we suspect a bug or we'not sure what's
going on.