changes to constraints must be inside animation block if one wants them animated.

The current code happens to work right now, but is liable to break in a future version of the operating system.
small cleanups - visual format language is usually clearer where it can be used.
Merge pull request #2 from kongtomorrow/master

Mostly fix the animated change of constraints outside of animation block. Also a couple small cleanups. (via @kongtomorrow)