Configure travis to run tests in --embedded-mode
Refactor to be more compliant with msgpack-RPC
Fix blocking rpc requests

It was possible to return from blocking rpc requests without a response, this
was fixed with some refactoring in client.py and rpc_stream.py
Use NVIM_SPAWN_ARGV instead of NEOVIM_SPAWN_ARGV for embedded tests
Merge pull request #22 from tarruda/msgpack-rpc-compliance

Msgpack rpc compliance