Merge pull request #120 from BU-CS673/graphics

Graphics -> Canfield
Merge pull request #122 from BU-CS673/graphics

Graphics -> Canfield
Merge pull request #134 from BU-CS673/production

Production -> Canfield
Merge pull request #135 from BU-CS673/production

Production -> Canfield
Fixed outdated javadoc comments in the Sprite classes
Renamed sound package to audio package
Merge pull request #139 from BU-CS673/production

Production -> Canfield
Added audio system interface; Added sound effects
Additional sound effect subsystem implementation
Added music & sfx directories
Implemented 3 sound effects
Additional Audio class implementation
Fixed multiple compile errors
Added javadoc comments to Audio system
Added all sound effect classes

Sound effects were specified in our 3/8 meeting:
https://groups.google.com/forum/#!topic/metcs673game/8PnNM5Cjsp0
Added sound effects to Sfx static class

- Added tests for all sound effects
- Small amount of additional documentation in Audio class
Wrote audio system tests
Added mute audio files for testing
Fixes to audio system; better error reporting
More fixes; Explanation for startStopMusic test

startStopMusic passes on its own, but fails when run with the other
audio tests. See the comment in the AudioTest.jav file for more
information on why this is. I will look into fixing this in the future.