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
Important refactors, introducing OpenBazaarContext to carry runtime configuration options. [WIP - still very unstable]

  - ioloop.install() redundancy cleanup, only installed once on openbazaar_daemon.

  - refactored ioloop's instantiation and startup out of openbazaar_daemon.start_node()
     as a new method 'start_ioloop()', invoked at the beginning of start_node() inside its
     own daemon thread.

  - New OpenBazaarContext object to hold all runtime configuration parameters and more
    runtime related information.

  - Argument parser now uses default values defined in getDefaults(),
    no need for repetition of these defaults, now can be maintained in a single place.

  - 'database' argument now parsed and used by OpenBazaarContext as 'db_path',
    this avoids confusion with a Obdb object. On the command line, users can still
    pass the --database parameter, irrelevant inside the codebase.

  - Periodic IP Checker for users trying to run on Tor now optional.
    Use runtime option '--enable-ip-checker' to enable periodic ip checking.

  - New parameter '--log-level' to change log verbosity.

  - Refactored signatures of MarketApplication.__init__, CryptoTransportLayer.__init,
    TransportLayer.__init__(), openbazaar_daemon.start_node(),

  - Removed code execution on openbazaar_daemon, argument parsing was redundant
    and this code will be (hopefully) unnecessary as we'll be getting rid of run.sh
    by the end of this feature branch.

  Had a chance to learn even more doing this, I may have some questions about the
  market_id when not specified. I couldn't find where it's generated @hoffmabc
start openbazaar_daemon in daemon thread, reuse defaults dictionary instance, pep8
trying to load libcrypto and libssl didn't work. When DYLD_LIBRARY_PATH is not set on osx, we'll just prompt help message and kill the process
Make sure database environments are setup correctly, including for development mode.

breakdown refactor on startup, OpenBazaarContext creation in its own method.
Updated transport tests, passing.
new --disable-stun-check option
Cleanup, new simplified "openbazaar" bash command

* Invoke node/openbazaar.py and gives back control to the user on the command
  line. Binaries for each platform will be necessary to invoke the python
  process that starts/stops OB.
Pure python launcher now equivalent to run.sh.

Just needs --config parameter to accept a configuration file on startup and I'll submit this
as a pull request to develop branch. pep8 compliant, all python tests pass.

Will also need to merge latest changes after this point, to make sure this will be easy to merge
with latest changes on master.

 - Supports development mode, launchers multiple instances, makes sure every instance has db setup. refactors.
 - configure.sh: make sure to use env/bin python tools, small refactor.
 - requirements.txt: fixed pystun requirement
 - openbazaar (posix CLI launcher) makes sure openssl library is in DYLD_LIBRARY_PATH if running on macosx.

 Fixes on transport.py:
 - commented out inet_pton calls. inet_pton wasn't actually
 doing anything except raise exceptions. in the event that
 inet_pton would actually work, its output was not being used
 to obtain the ip in raw network format anyways.
 - now when we shutdown transport, we make sure the zmq event
 stream is closed properly.
 - in case the market_id is different after we load the settings
 we make sure the OpenbazaarContext object knows is updated.
 - ipv4.icanhazip.com fix on periodic callback updater (fixed merged from master branch)
Search pylint from virtualenv bin.
Style fixes.