Changed upgrade ratios to be a bit more reasonable.

For simplicity, towers are currently locked at Single L2, Area L3, and Status L1. I'll add upgrade functionality in a bit.
Merge branch 'master' of https://github.com/bschalich/TowerDefense

Conflicts:
	js/tower.js
Merge branch 'master' of https://github.com/bschalich/TowerDefense

Conflicts:
	js/tower.js
Slowed down the shoot animation, so we can see the bullets. Fixed the upgrade levels, because assets for L2,3 of stoneRanged don't exist yet.