Merge pull request #37 from bombela/master

Compile & run examples with latest rust and zmq 4.1.0
update to rust HEAD
cargo-ify rust-zmq
add Cargo.toml
Remove redundent zmq_msg_close

Per: http://api.zeromq.org/4-1:zmq-msg-close
zmq_msg_close after a zmq_msg_send is not necessary.
send() for msgs, send_bytes() for bytes
Remove workaround no longer necessary