Refs #1, add a basic socket task.
Refactor, renames, and removing req.rs for now, refs #1
Rename handle() to in_event()
Added base stream_engine.rs, make SocketBase to exit on only critical
closed endpoints.
Added options.rs
zmtp 2.0 handshake
fn handshake() and TODO comments
Socket type in options and sent during handshake.
Added decoder.rs and msg.rs, can now receive simple messages. Also:

 * use map_err to replace wrap_io_error
 * added options.maxmsgsize
Fixed #2, a basic fifo msg_recv interface
Fix license in meta tag.
Rename `chan`s to more reasonable names
Merge pull request #1 from zeromq/master

Update with upstream