Initial commit.

Connect to neovim server.
Get API list.
Learn NeoServer::RESPONSE, NOTIFY.
Remove server_address().
clerification
Update for msgpack branch poc/0.6.
UnixSocket::recv_msgpack().
Give the msgpack::unpacker to NeoServer.

Fixes memory invalidation.
UnixSocket -> Socket module.
Simplify msgpack code.
Send/recieve one command-no args.
Shorted NeoServer::request().

Default the second argument to { }, or 'no args'.
Squash NeoServer::request() and get_response().
socket_error_msg -> Socket module.
Simple one-shot prompt. Int-args only.
Be back-campat with msgpack-c/master.
Simple looping prompt. Type "quit" to exit.
words: handle quotes, escapes, and errors.

Change the signature to accept an insertion iterator so that we can
return a WordsError. Alter main() to respect the use of iterators and
handle the errors generated by words().
Request API data in NeoServer's ctor().
Call functions by name or number.
Send args as bool if 'true' or 'false'.