Fixed bug with SceneCache animated object topology.

Previously, if the first topology hash matched the last topology hash, the animatedObjectTopology attribute would not be written, even if the hashes on the intermediate frames differed.
iterate active compilers
Merge pull request #222 from richardmonette/activeCompilers

iterate active compilers
Merge pull request #221 from andrewkaufman/changingTopoBug

Fixed bug with SceneCache animated object topology.