The following changes are made:
`jupyter-initialize-connection` -> `jupyter-comm-initialize`
`jupyter-connect-client` -> `jupyter-comm-add-handler`
`jupyter-disconnect-client` -> `jupyter-comm-remove-handler`
`jupyter-comm-client-loop` -> `jupyter-comm-handler-loop`
* README.org: Do it.
* jupyter-channel-ioloop-comm: Do it.
* jupyter-client.el: Do it.
* jupyter-comm-layer.el: Do it.
(jupyter-comm-layer): Rename `clients` slot to `handlers`. Update all uses.
* jupyter-kernel-process-manager.el: Do it.
* jupyter-repl.el: Do it.
* jupyter-server.el: Do it.
* jupyter-zmq-channel-comm.el: Do it.
* test/jupyter-server-test.el: Do it.
* test/jupyter-test.el: Do it.
Since we are using keyword to represent channels on the client level, use a
plist of channels on the comm layer level instead of channel slots. This allows
us to remove `jupyter-comm-channel` and simplify the relevant code somewhat.
* jupyter-channel-ioloop.el (jupyter-zmq-channel): Require.
(jupyter-channel-ioloop-add-start-channel-event): `sync` -> `zmq`
* jupyter-comm-layer (jupyter-comm--channel): Moved from `jupyter-channels.el`.
* jupyter-kernel-manager.el: `sync` -> `zmq`
* jupyter-zmq-channel-comm.el: New file.
* jupyter-channels.el: Mostly renamed to jupyter-zmq-channel.el. The
`jupyter-channel` class was moved to `jupyter-channel.el`. All that remains are
those classes dependent on `zmq`.
* test/jupyter-test.el: `sync` -> `zmq` where appropriate.
Extract `jupyter-channel` class from `jupyter-zmq-channel.el` into its own file
