add uniqueness constraint to provider and username
adding a meta tag to prevent crawling
Simplify OmniAuth auth stubbing

There is now a single file that is responsible for defining and enabling
OmniAuth stubs. Furthermore, authentication in feature specs is more
explicit with regard to which user is signed in, and configures OmniAuth
so that the about-to-be-signed-in user can sign in via Chef and can link
her GitHub account

Conflicts:
	spec/spec_helper.rb
Merge pull request #329 from opscode/unique-account-provider

Make the provider/username combo unique
Remove index on User email
Authenticate users by their Chef username
Remove the now-unused User.with_email scope
Update Chef Account information on authentication
Merge pull request #330 from opscode/no-crawling-plz

Adding a meta tag to prevent crawling
Merge pull request #331 from opscode/non-unique-email-addresses

Email addresses need not be unique.
owners shouldn't be able to add themselves as collaborators
style the button consistently
add name to collaborator
find users by username
Formats the add collaborator input field
Override some default select2 styles and convert to rem-calc for RWD.
find users by username, for reals this time
allow cookbook owners to transfer that ownership to a collaborator
rename transfer_ownership to transfer