rewrite Crafty.unbind

see discussion at issue 417 --
https://github.com/craftyjs/Crafty/issues/417
add unit tests

Add tests to confirm Crafty.bind and Crafty.unbind behavior;
Add unit test for Crafty('*') [which currently fails, a known issue];
Force tests to run in order; they were not written atomically;
Add note to developers for how to run these tests conveniently.
Merge pull request #420 from sbyrnes321/unbind

rewrite Crafty.unbind
core unit-tests cleanup

* Use atomic (i.e. self-contained) tests.
* Fix typos that caused recently-added tests to erroneously fail.
* Consistent whitespace (tabs only).
* Always use strictEqual instead of equal, to avoid false-negatives.

All tests pass right now except the SAT overlap test, which is
-13.858192987669298 instead of -18.47759.
(The test was already failing before -- I didn't change anything.)
fix leakage of global variable from forgotten "var"

fix leakage of global variable from forgotten "var" (revealed by QUnit)