Noah Levenson

There's been some important bug fixes.

Before returning early from the `Discover` function, you have to drain the `FilterDiscovDone` channel, otherwise it leaks `discoverFilteringBehavior` goroutines.

The missing returns here create a blocked send on `receivedCh` which cause the goroutine to hang open indefinitely.

When importing `github.com/enobufs/go-nats/nats` as a library and compiling my program with the `-race` flag, I consistently received the following data race warning: ``` ================== WARNING: DATA RACE Write at 0x00c0001cf4c0...