Added bg command to the help menu
Merge pull request #2 from NullMode/dev

Added bg command to the help menu
CONTRIBUTORS file and prompt
* CONTRIBUTORS
  -- official recognition of contributions to zarp
* src/core/session_manager.py
  -- unifying y/n selections
Fixed a bug when threads fail to die
* zarp.py
  -- Sometimes a module's spawned threads don't cleanly die.  So long as
  the module is shutdown, though, we should be safe to quit.
* src/core/stream.py
  -- Fixed a bug in get_session_count; now more accurately detects the
  number of running sessions.
New BeEF injection module
* src/modules/attacks/__init__.py
  src/modules/attacks/beef_hook.py
  -- Injects BeEF hooks into ARPP traffic.  See wiki for more
  information about this.
* src/modules/attacks/attack.py
  -- Abstract attack
* src/lib/libmproxy
  -- A fantastic library, and something I've been dancing around adding.
  This library will come in handy for plenty of other future modules.
* src/modules/sniffer/packet_modifier.py
  -- Removed this module; too buggy, and should be rewritten without the
  use of nfqueue