Merge pull request #3 from garethleonard/master

Entity stuff
added title and menu buttons to buttons folder in rscs
Player movement, missiles implemented
Asteroids spawning to Level1State
Merge pull request #4 from dallinray1/master

added title and menu buttons to buttons folder in rscs
added lv2 bg, added asteroid break chunks & explosions, added fade menu buttons
edited button
improved bgs
Missile spawn location and velocity bugs fixed
Merge branch 'master' of git@github.com:klords/ser-215-asteroids.git
Merge pull request #5 from dallinray1/master

improved resources
Added damage property to Missile class for boss fights
Passed missileDamage to missile constructor. Moved shoot and
removeMissile methods to bottom of methods. Added getter for lives (for
HUD and gameStateManager use).
updated debris Field
Corrected image size (154px -> 150px)
MenuState completed (debris field added to background, buttons
implemented)
Misc cleanup and bugfix in Asteroid (nullpointer at g.transform(at) when
entering level 1 due to at not being set).
Took out debug messages from DebrisField class
Added LevelState superclass. Modified constructors and calls to
Level1State. Also misc cleanup in GameState and GameStateManager.
Player can collide with and shoot/destroy asteroids. However, collisions
are buggy right now. Debugging spawning, so have a few debug messages in
the PlayerShip class.