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
Ethan Buchman
Anton Kaliaev
Jae Kwon
Ethan Frey