* GetByHeight will now switch to using binary search once
we have  >=50 items.
* Feedback from @ebuchman to catch a missed spot where
we forgot about lazy sorting that the original code
assumed would always have sorted commits by height.
Added a lazy sorting routine here too.
A test as well to ensure that we always get the properly
sorted and last value.

Addressing PR review requests from @melekes and @ebuchman to
add a test that checks that the heights returned from both are
the same thus providing a perceptible equivalence of the code
linear range search vs binary range search code.

Also lazily load the commits to only be run once when
the benchmarks are activated, lest it slows down all the tests

Updates #1021

* Implement a GetHeightBinarySearch method that looks for
the height using the binary search algorithm guaranteeing
worst case iteration time of O(log2(n))
whereas
worst case iteration time of O(n) for the current linear search

So if n we had 500 commits stored by height and sorted, to
trigger the worst case scenario for each, pass in
the most negative height you can find e.g. -1
Linear search: 500 iterations
Binary search: 9 iterations

with n=1000, qHeight = -1
Linear search: 1000 iterations
Binary search: 10 iterations

with n=1e6, qHeight = -1
Linear search: 1e6 iterations
Binary search: 20 iterations

Of course there are realistic expectations e.g. a max of
commits that may be saved so linear search might be useful
for very small size set because it has less preparing overhead
and only ~2 types of comparisons, but nonetheless binary search
shines as soon as we start to hit say 50 commits to search from
as you can see below:

```shell
$ go test -v -run=^$ -bench=MemStore
goos: darwin
goarch: amd64
pkg: github.com/tendermint/tendermint/lite
BenchmarkMemStoreProviderGetByHeightLinearSearch5-4     300000        6491 ns/op      1600 B/op       15 allocs/op
BenchmarkMemStoreProviderGetByHeightLinearSearch50-4      200000       12064 ns/op      1600 B/op       15 allocs/op
BenchmarkMemStoreProviderGetByHeightLinearSearch100-4      50000       32987 ns/op      1600 B/op       15 allocs/op
BenchmarkMemStoreProviderGetByHeightLinearSearch500-4       5000      395521 ns/op      1600 B/op       15 allocs/op
BenchmarkMemStoreProviderGetByHeightLinearSearch1000-4	       500     2940724 ns/op      1600 B/op       15 allocs/op
BenchmarkMemStoreProviderGetByHeightBinarySearch5-4     300000        6281 ns/op      1600 B/op       15 allocs/op
BenchmarkMemStoreProviderGetByHeightBinarySearch50-4      200000       10117 ns/op      1600 B/op       15 allocs/op
BenchmarkMemStoreProviderGetByHeightBinarySearch100-4     100000       18447 ns/op      1600 B/op       15 allocs/op
BenchmarkMemStoreProviderGetByHeightBinarySearch500-4      20000       89029 ns/op      1600 B/op       15 allocs/op
BenchmarkMemStoreProviderGetByHeightBinarySearch1000-4	      5000      265719 ns/op      1600 B/op       15 allocs/op
PASS
ok    github.com/tendermint/tendermint/lite 86.614s
$ go test -v -run=^$ -bench=MemStore
goos: darwin
goarch: amd64
pkg: github.com/tendermint/tendermint/lite
BenchmarkMemStoreProviderGetByHeightLinearSearch5-4     300000        6779 ns/op      1600 B/op       15 allocs/op
BenchmarkMemStoreProviderGetByHeightLinearSearch50-4      100000       12980 ns/op      1600 B/op       15 allocs/op
BenchmarkMemStoreProviderGetByHeightLinearSearch100-4      30000       43598 ns/op      1600 B/op       15 allocs/op
BenchmarkMemStoreProviderGetByHeightLinearSearch500-4       5000      377462 ns/op      1600 B/op       15 allocs/op
BenchmarkMemStoreProviderGetByHeightLinearSearch1000-4	       500     3278122 ns/op      1600 B/op       15 allocs/op
BenchmarkMemStoreProviderGetByHeightBinarySearch5-4     300000        7084 ns/op      1600 B/op       15 allocs/op
BenchmarkMemStoreProviderGetByHeightBinarySearch50-4      200000        9852 ns/op      1600 B/op       15 allocs/op
BenchmarkMemStoreProviderGetByHeightBinarySearch100-4     100000       19020 ns/op      1600 B/op       15 allocs/op
BenchmarkMemStoreProviderGetByHeightBinarySearch500-4      20000       99463 ns/op      1600 B/op       15 allocs/op
BenchmarkMemStoreProviderGetByHeightBinarySearch1000-4	      5000      259293 ns/op      1600 B/op       15 allocs/op
PASS
ok    github.com/tendermint/tendermint/lite 86.204s
```

which gives
```shell
$ benchstat old.txt new.txt
name                               old time/op    new time/op    delta
MemStoreProviderGetByHeight5-4       6.63µs ± 2%    6.68µs ± 6%   ~             (p=1.000 n=2+2)
MemStoreProviderGetByHeight50-4      12.5µs ± 4%    10.0µs ± 1%   ~             (p=0.333 n=2+2)
MemStoreProviderGetByHeight100-4     38.3µs ±14%    18.7µs ± 2%   ~             (p=0.333 n=2+2)
MemStoreProviderGetByHeight500-4      386µs ± 2%      94µs ± 6%   ~             (p=0.333 n=2+2)
MemStoreProviderGetByHeight1000-4    3.11ms ± 5%    0.26ms ± 1%   ~             (p=0.333 n=2+2)
```

If need be we can make a hybrid algorithm that switches between the
linear and binary search depending on the number of items.
This is reminiscent of Python's TimSort algorithm.

improve error message

Fix documentation typos

Fix Vagrantfile

If you get an error, please run `vagrant box update`.

p2p/conn: fix blocking on pong during quit and break out of loops

consensus: fix SetLogger in tests

p2p: add Channels to NodeInfo and don't send for unknown channels

call FlushSync before calling CommitSync

WIP: docs consolidation

p2p: bust up into sub dirs

StopPeerForError in blockchain and consensus

mercy for developers with slow Internet

if we call it after, we might receive a "fresh" transaction from
  `broadcast_tx_sync` before old transactions (which were not
  committed).

Refs #1091

```
Commit is called with a lock on the mempool, meaning no calls to CheckTx
can start. However, since CheckTx is called async in the mempool
connection, some CheckTx might have already "sailed", when the lock is
released in the mempool and Commit proceeds.

Then, that spurious CheckTx has not yet "begun" in the ABCI app (stuck
in transport?). Instead, ABCI app manages to start to process the
Commit. Next, the spurious, "sailed" CheckTx happens in the wrong place.
```

Small fix in example