Only apply masonry JS to index pages, widen `.box`es on permalink pages.
Add permalink page HTML mockups for all, photo, and text post types.

This commit adds three new HTML mockups, although one is merely a
convenience template. Specifically, `web/permalink.html` provides a
single file in which all post types can be prototyped. The
`web/permalink-photo.html` and `web/permalink-text.html` files showcase
the desired Tumblr-generated markup for a permalink page of the photo or
text post type, respectively.
Remove "Your photos" heading from permalink post types except "photo".
Merge branch 'master' into tumblr
Apply CSS from merge.
Conditionally print `IndexPage` class.
Conditionally show "Your photos" heading (photo permalinks & indexes).