CSP channels implementation

I've had some chat with @coding-horror over Twitter and concurrent-ruby was brought again to my mind, so I went on to look for the channel implementation, which I found to be lacking. Turns out I've had some implementation collecting dust, so maybe someone over here could make use of this.

I strived to keep the implementation simple, keeping the Go spirit while still being idiomatic Ruby: take a look at the examples and open the corresponding Go by Example page.

The implementation is almost feature complete save for non-blocking select, for which I'm still looking for a straightforward and idiomatic syntax.

Anyway, feel free to ignore this if you don't feel like it's fit for this project.