* Add a text formatter interface used by EditingText. Provide some default implementations.
* self nits
* Handle -1 selection offsets
* review notes
* simplify regular expression
* Add whitelisting formatters. Use a custom phone number formatter in text demo.
* review notes
* not being able to addAll(null) is pretty annoying
* review notes
* partial tests
* Add tests
* didn’t end up needing mockito
* move to services