Adding Support For Meta & Stats Commands

[moh-stripe]

Adds new functionality for Meta commands, which provides more flexibility with the use of in-line flags, and the stats commands which returns information for each connection. There are also tests for each of these commands.

[dormando]

I checked the context of this PR: it might be useful as reference but their own client has changed significantly since this.

We have several implementations of the meta protocol to choose from at this point, but we'll need to look at it as what's best for Go here.