async C client library for NSQ

This is currently pretty low-level, but functional. The raw building blocks for communicating asynchronously via the NSQ TCP protocol are in place as well as a basic "reader" abstraction that facilitates subscribing and receiving messages via callback.

TODO:

• maintaining RDY count automatically
• feature negotiation
• better abstractions for responding to messages in your handlers

• libev
• libevbuffsock