Update coffee-rails
Use Markdown for body text in views
Remove duplicate root path navigation link
Move hero unit outside of main container
Move the home#welcome action to home#index
Remove extraneous text from front page
Clean up views

Title and page header helpers were confusing and didn't add much, so
they were removed, and the page header moved into the template.

A nav_item_link_tag helper has been added, which nests a link within a
list item with an "active" class when current.