simplify rectangle separation test to improve performance

i've put together ad hoc tests to ensure the intersects method is still functioning as expected, and they [show speed ups of about 28%](https://github.com/LoomSDK/LoomSDK/commit/7012e6b#commitcomment-7861575):

* [baseline](https://github.com/ellemenno/LoomSDK/tree/PBG-rect-intersect-baseline/tests/RectangleIntersectsTest)
* [improved](https://github.com/ellemenno/LoomSDK/tree/PBG-rect-intersect-sat/tests/RectangleIntersectsTest)

..but i haven't been able to figure out how to get the loomlibs rejiggered to allow proper unit testing:
http://loomsdk.com/forums/feedback/topics/unittest-framework-for-loomscript/posts/5230