Basic spec
Raise an error when Celluloid::ZMQ hasn't been initialized, instead of lazily initializing init

Lazy initialization is not thread safe. If the user forgets to call `init`, we want to fail fast instead of possibly creating thread safety problems.
Fix docs
Add a basic spec for testing a REP socket
Make sure waker is shut down. Fixes mailbox specs

Requires celluloid/celluloid#376
Add a spec which checks pipelining of tasks when using ZMQ sockets
Re-add option to set context manually
Add spec which tests writing to sockets
Use inproc instead of TCP, so we don't have to mess around with open ports
Merge pull request #32 from jnicklas/specs

Add basic specs