Start of unified 'openbazaar [options] <command>' python based launcher script.

 - added pystun as a pip requirement
 - Gets external IP (UDP: port) using STUN servers.
 - Checks if DYLD_LIBRARY_PATH has been set on MacOSX, if not
   gives a warning and tries to ammend by manually loading
   libssl.dylib and libcrypto.dylib if found at `brew --prefix openssl`.
 - default configuration values loaded into a dictionary that will
   be used on the rest of the launching script.
 - OpenBazaar is launched and P2P port used is dynamic and based on the port reported as available via STUN.
   however, I'll try to use multiprocessing so that the code runs on a separate process
   and we can return control back to the user on the terminal's process.

 STILL TO BE DONE:
   - porting seeding mode logic from run.sh
   - porting development mode logic from run.sh (using setup_db here)
   - implementing shutdown websocket or http handler, and being able to send a websocket request.
   - implementing a status websocket or http handler to print the status of the servent