Move page-level comments to the bottom

If they’re at the top and somebody goes to the page just to look at the
file and not at the comments, a huge discussion at the top can be very
distracting.

We assume that people will go to pages more often to see the
files/diffs/commits than to look at comments.
Add source maps for Backbone and Underscore
Remove the line-comment template

Wasn’t used anywhere