send -> send_bytes (+ update for latest rust)

- send is renamed send_bytes
- a new version of send handles zmq messages

Note that I defined send as:

    pub fn send(&mut self, msg: Message, flags: int) -> Result<(), Error>

A zmq_msg is consumed by zmq once it given to zmq_send(). This maps nicely to rust by taking Message by value, which cannot be copied, only moved.

 - a bunch of random fixes to match the latest rust
 - notably, I casted all posix88 enums to int in order to typecheck. Not sure if it is the best idea (and it looks ugly for sure)