Revert "Merge pull request #18 from ming13/android-textutils"

Despite that fact that every method in the library calls into Android, we don't actually want to rely on an Android implementation for any behavior. Theoretically the user could be mocking the methods or providing their own subclasses which return actual values.

Refs #18.

This reverts commit fd1eed5e9e643462a249a5234d91ace2507f53e0, reversing
changes made to e03b6dcf1d02fc549c1e62e4e41286ff71fa1252.
Merge pull request #40 from square/jw/revert

Revert "Merge pull request #18 from ming13/android-textutils"