Update Guard documentation
Add proper integration tests for automatic mailer
Automatic didn't turn out to be so inflexible after all
Add Rails 4.1 integration spec + instructions on how to add new versions
Add a quick upgrade guide
Crash when trying to assign unknown keys to Options

This should help people in case they have spelling errors in their
configs. Spelling errors are usually very hard to see and are
frustrating to debug.
Prepare a 1.0.0-pre1 release