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.