We can make the implementation more robust by adjusting our assumptions
and leverage explicit file modes for syncing. Additionally we going to
assume that we want to clean up and can't really recover if thos
operations (file close and removal) fail.

* utilise file mode for majority of concerns
* improve test coverage by covering more assumptions
* signature parity with ioutil.WriteFile
* always clean up

Replaces #160

Fixes #169
Fixes https://github.com/tendermint/tendermint/issues/1322

The previous code was very trusting assuming that
rational actors will use this code. However, Byzantine
actors don't care and in the case of the linked issue
negative lengths can be sent to this code unfettered
having been received from a peer.

This code is essentially just a sign change from
`==`
to
`<=`

and we've gutted out that attack by being more defensive.

update version, changelog

Simplify WriteFileAtomic

* Implement better Parallel

We can make the implementation more robust by adjusting our assumptions
and leverage explicit file modes for syncing. Additionally we going to
assume that we want to clean up and can't really recover if thos
operations (file close and removal) fail.

* utilise file mode for majority of concerns
* improve test coverage by covering more assumptions
* signature parity with ioutil.WriteFile
* always clean up

Replaces #160

Fixes #134

Those functions are unused in the whole Tendermint Github
organization plus they were unnecessariy verbose and could
have been concisely replaced with

```go
func RightPadString(s string, totalLength uint) string {
       return fmt.Sprintf("% *s", totalLength, s)
}

func LeftPadString(s string, totalLength uint) string {
       return fmt.Sprintf("% -*s", totalLength, s)
}
```

delete them anyways

Fixes #169
Fixes https://github.com/tendermint/tendermint/issues/1322

The previous code was very trusting assuming that
rational actors will use this code. However, Byzantine
actors don't care and in the case of the linked issue
negative lengths can be sent to this code unfettered
having been received from a peer.

This code is essentially just a sign change from
`==`
to
`<=`

and we've gutted out that attack by being more defensive.

* common/random.go supports seeding and *Rand
* Ensure determinism

* encodeByteSlice uses uvarint for length instead of varint
* Implemented NewPrefixDB
* Fix flowrate test (#165)
* Complete implementation and fix tests
* Add tests for MemBatch Write[Sync]

v0.7.0 (aka "sdk2")

minor nit

add Quit method to Service interface

remove deprecated QuitService

fix RepeatTimer memory leak (Refs #137)

* test case

* drain channels on reset

Leaking memory:
```
leaktest.go:144: leaktest: leaked goroutine: goroutine 116 [chan send]:
        github.com/tendermint/tmlibs/common.(*RepeatTimer).fireRoutine(0xc42006a410, 0xc4203403c0, 0xc42031b2c0)
                /go/src/github.com/tendermint/tmlibs/common/repeat_timer.go:160 +0x6e
        created by github.com/tendermint/tmlibs/common.(*RepeatTimer).reset
                /go/src/github.com/tendermint/tmlibs/common/repeat_timer.go:196 +0xe9
```

The alternative solution could be draining channels on the client side.

* add one more select instead of draining

thanks to Jae

add waitCh as an alternative to waitGroup

common/BitArray: reduce fragility with methods

Fixes https://github.com/tendermint/tmlibs/issues/145
Fixes https://github.com/tendermint/tmlibs/issues/146

The code in here has been fragile when it comes to nil
but these edge cases were never tested, although they've
showed up in the wild and were only noticed because
the reporter actually read the logs otherwise
we'd have never known.

This changes covers some of these cases and adds some tests.

common: IsHex should be able to handle 0X prefixed strings

new methods:
 - [CList] WaitChan()
 - [CElement] NextWaitChan()
 - [CElement] PrevWaitChan()

Refs https://github.com/tendermint/tendermint/pull/1173

merkle: remove go-wire dep by copying EncodeByteSlice

IsHex should also successfully decode strings prefixed with
0X instead of only 0x strings.

Also add tests generally for IsHex.

Merge sdk2 into develop

Sdk2 hashers and simple map