Enable caching for bundler in Travis
Fix the file extension of the devise_invitable migration
Use letter_opener for dev mail

[ci skip]
Run db:migrate, updates schema.rb
Background color is set for the whole page

And authform can grow up to 50% of the page width
Replace devise views with simple_form variants
Drop registrable, set up lockable
Horizontally align extra devise navigation links

Unfortunately, by making the li elements inline (to achieve the horizontal
layout) the list styles are forcibly removed, so I have to resort to li:after
content. I'm not happy about having to do that, but it does make it look pretty
neat!
Rewrite the sign in form to use .authform

This styling is based on the original RailsApp style.
Rewrite the rest of devise views to use authform
BEWARE THE BABELFISH
Don't use bin/rake, just search $PATH