Adds a builtin flip animation as requested via https://jira.appcelerator.org/browse/TC-2750
Added instruction for flip animation.
Added documentation and error informing flip-animation is iOS-only.
[ALOY-792] some doc fixes, test case, _generated files update
Merge pull request #225 from appcelerator/pr/223

[ALOY-792] Add flip animation to animate builtin