Sprite animation

#Changes#
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###Added the jquery plugin file for spritely - not being used yet
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###Created sprite sheets for running forwards and backwards, and sprites for facing forwards, backwards, and jumping
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###Created new js file for sprite animation
- keydown for left arrow - faces sprite backwards - animates sprite sheet if held down
- keydown for right arrow - faces sprite backwards - animates sprite sheet if held down
- keyup for left/right arrow - removes run/animation classes
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###main.scss
- added classes for sprite
	- facing forward
	- facing backward
	- running forward sprite sheet
	- running backward sprite sheet
- added class for sprite animation - 'sprite-animate' keyframe
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###index.html
- added sprite div - initializes with sprite facing forward
- commented out 'controls.js' to not interfere with 'sprite-animation.js' during testing