* Instead of having a fixed sleep duration, start a thread
that monitors the subprocess.
* Started thread is joined, if process finishes thread returns
before timeout.
* Should increase speed and reduce overhead on CPU.
* Refactor Command class for easier reading.
* Some other minor clean ups & method renames.
* Change travis to use `env` and `matrix` to select builds.
* Use case instead of ifs to select behaviour.
* Buffer updates now managed by __main__ loop with buf_q.
* Synchronous neovim install temporarily provided by python installer.
* Known issues:
* No ctrl-c/interrupt support on nvim.
* Graphical bug: https://github.com/neovim/python-client/issues/103
* Main differences from ruby are inside Command class, notably it
poll/sleeps on the subprocess to check output & timeout.
* Another difference, interrupt is not instaneous due to checking var.
* Otherwise, I mainly just mirrored code into objects.
* Note that due to GVim freeze, disabling use on Windows
