Remove unused ReadFile (unused) and
WriteFile (almost unused, alias of ioutil.WriteFile).

Add testcases for Must{Read,Write}File.

* Fix many golint errors

* Fix golint errors in the 'lite' package

* Don't export Pool.store

* Fix typo

* Revert unwanted changes

* Fix errors in counter package

* Fix linter errors in kvstore package

* Fix linter error in example package

* Fix error in tests package

* Fix linter errors in v2 package

* Fix linter errors in consensus package

* Fix linter errors in evidence package

* Fix linter error in fail package

* Fix linter errors in query package

* Fix linter errors in core package

* Fix linter errors in node package

* Fix linter errors in mempool package

* Fix linter error in conn package

* Fix linter errors in pex package

* Rename PEXReactor export to Reactor

* Fix linter errors in trust package

* Fix linter errors in upnp package

* Fix linter errors in p2p package

* Fix linter errors in proxy package

* Fix linter errors in mock_test package

* Fix linter error in client_test package

* Fix linter errors in coretypes package

* Fix linter errors in coregrpc package

* Fix linter errors in rpcserver package

* Fix linter errors in rpctypes package

* Fix linter errors in rpctest package

* Fix linter error in json2wal script

* Fix linter error in wal2json script

* Fix linter errors in kv package

* Fix linter error in state package

* Fix linter error in grpc_client

* Fix linter errors in types package

* Fix linter error in version package

* Fix remaining errors

* Address review comments

* Fix broken tests

* Reconcile package coregrpc

* Fix golangci bot error

* Fix new golint errors

* Fix broken reference

* Enable golint linter

* minor changes to bring golint into line

* fix failing test

* fix pex reactor naming

* address PR comments

* Clean up `fail.go`

- Clean up fail.go
- Remove unneeded Func `FailRand()`

closes #2729

Signed-off-by: Marko Baricevic <marbar3778@yahoo.com>

* add in commented lines

* privval: more info in errors

* wal: change Debug logs to Info

* wal: log and return error on corrupted wal instead of panicing

* fail: Exit right away instead of sending interupt

* consensus: FAIL before handling our own vote

allows to replicate #3089:
- run using `FAIL_TEST_INDEX=0`
- delete some bytes from the end of the WAL
- start normally

Results in logs like:

```
I[2019-02-03|18:12:58.225] Searching for height module=consensus wal=/Users/ethanbuchman/.tendermint/data/cs.wal/wal height=1 min=0 max=0
E[2019-02-03|18:12:58.225] Error on catchup replay. Proceeding to start ConsensusState anyway module=consensus err="failed to read data: EOF"
I[2019-02-03|18:12:58.225] Started node module=main nodeInfo="{ProtocolVersion:{P2P:6 Block:9 App:1} ID_:35e87e93f2e31f305b65a5517fd2102331b56002 ListenAddr:tcp://0.0.0.0:26656 Network:test-chain-J8JvJH Version:0.29.1 Channels:4020212223303800 Moniker:Ethans-MacBook-Pro.local Other:{TxIndex:on RPCAddress:tcp://0.0.0.0:26657}}"
E[2019-02-03|18:12:58.226] Couldn't connect to any seeds module=p2p
I[2019-02-03|18:12:59.229] Timed out module=consensus dur=998.568ms height=1 round=0 step=RoundStepNewHeight
I[2019-02-03|18:12:59.230] enterNewRound(1/0). Current: 1/0/RoundStepNewHeight module=consensus height=1 round=0
I[2019-02-03|18:12:59.230] enterPropose(1/0). Current: 1/0/RoundStepNewRound module=consensus height=1 round=0
I[2019-02-03|18:12:59.230] enterPropose: Our turn to propose module=consensus height=1 round=0 proposer=AD278B7767B05D7FBEB76207024C650988FA77D5 privValidator="PrivValidator{AD278B7767B05D7FBEB76207024C650988FA77D5 LH:1, LR:0, LS:2}"
E[2019-02-03|18:12:59.230] enterPropose: Error signing proposal module=consensus height=1 round=0 err="Error signing proposal: Step regression at height 1 round 0. Got 1, last step 2"
I[2019-02-03|18:13:02.233] Timed out module=consensus dur=3s height=1 round=0 step=RoundStepPropose
I[2019-02-03|18:13:02.233] enterPrevote(1/0). Current: 1/0/RoundStepPropose module=consensus
I[2019-02-03|18:13:02.233] enterPrevote: ProposalBlock is nil module=consensus height=1 round=0
E[2019-02-03|18:13:02.234] Error signing vote module=consensus height=1 round=0 vote="Vote{0:AD278B7767B0 1/00/1(Prevote) 000000000000 000000000000 @ 2019-02-04T02:13:02.233897Z}" err="Error signing vote: Conflicting data"
```

Notice the EOF, the step regression, and the conflicting data.

* wal: change errors to be DataCorruptionError

* exit on corrupt WAL

* fix log

* fix new line

original author of this file is @ebuchman:

https://github.com/ebuchman/fail-test