Rename Notifier to UserMailer It's a convention in rails to name your mailers with a Mailer suffix, and is also common to name the class after the recipient (e.g. User, Admin). So UserMailer seems a reasonable choice.
erblint: fix remaining single quoted strings
Whitespace fixes for notifier erb views
Remove that ugly style="margin: 0" It's really only needed for rendering in Yahoo. Let's try to do without having to copy-paste that into every html template.
Simplified the partial layout Rather than wrap the body in a :body block, just make it the default, unnamed block, which keeps the markup more lightweight.
Dressed up gpx notification mails
Rename views to rails 2 style names.