Added back many of the previously commented out tests, some of them have been changed significantly however.

Removed the unicode future import, moving over to manually implementing this. Should fix the python2 version, or get us a bit closer.

Added some dependencies in tox. Reenabled the httpretty dependent tests on 2.7 only. Fixed some bugs in the APRS-IS portion of the code revealed from the unit tests.

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.