Add contribution guidlines

These are guidelines, not necessarily a rulebook.
Add (temporary terrible) volume controls

 - Add volume control

   These volume controls are basically nothing more than sliders.  They
   look terrible and hopefully will be as temporary as they are
   terrible.

 - Allow saving of specific non-user sources via obs_load_source and
   obs_save_source functions.

 - Save data of desktop/mic audio sources (sync data, volume data, etc),
   and load the data on startup.

 - Make it so that a scene is created by default if first time using the
   application.  On certain operating systems where supported, a default
   capture will be created.  Desktop capture on mac, particularly.  Not
   sure what to do about windows because monitor capture on windows 7 is
   completely terrible and is bad to start users off with.