Improve checkColliders and add 'left'

this.checkColliders
-add x = child[index];
-replace child[index] to x

this.create
-add res.size = 0;
-add res.baseIndex = 0;
-implement part of the 'left' arrangement
Merge pull request #2 from gastonci/rebranch

Improve checkColliders and add 'left'