Adding initial code for Apex project. It connected to two TNC, sends a beacon, sends a status, and digipeats. Just needs to be turned into a workable app.

- Abstracted APRS-IS TCP server connect logic out into `APRS.connect()`,
  which must be called before you send or receive from APRS-IS.
- Added support for APRS-IS Send-only on HTTP & UDP, as well as
  send/receive on HTTP.
- Linted, PEP8'd and cleaned up code.
- Updated docs.
- Updated docstrings & Copyrights.