Groundwork for the library

The icon is blatantly stolen from r/pebble flair and probably temporary.
Aaand first commit screwup.
Groundwork for the test app.
Implementation of the "transport protocol"

Basic and untested, without any error handling - although mostly that
should be done higher up the tree, I think.
Implemented message sending

Again, untested.
Basic setup for the Pebble class
"Ping" functionality implemented.

There's probably a much better way to handle waiting for an asynchronous
process than what I've done here.
Endpoint-specific events are handled Differently.