allow multiple categories in a "_category" url

If multiple categories are placed in the path of a "_category" URL, separated by "/" characters, the request will return a page listing all pages that contain all of the categories.
using all instead of intersect for test
replacing splitOn with wordsBy, using comma as sep
adding filter links for _category pages
Merge pull request #422 from wcaleb/multi_category_url

allow multiple categories in a "_category" url
Fixed image export for DOCX, RTF, slides, etc.

Still broken for PDF.

See #399.
Fixed images in PDF export.

See #399, #353.
Restored inline syntax highlighting.

Closes #399.
Added beamer as export format.

Closes #391.
Add github-style backgrounds to code blocks
A previous commit (9698018e) broke redirect functionality; this fixes it.
Lighter Heading Border

This makes the heading line the same color as wikimedia's.
Fixed links on activity page:

 * Links for pages were broken (by 0548c1a7) because the ".page" wasn't being stripped from the URL
 * Links for binary files now link to the appropriate revision (and handleAny now checks the revision parameter)
Merge pull request #431 from duairc/fix-activity-page-links

Fixed links on activity page
Merge pull request #429 from duairc/fix-redirects

A previous commit (9698018e) broke redirect functionality; this fixes it.
Merge pull request #430 from joehillen/heading-border-color

Lighter Heading Border
Merge pull request #424 from joehillen/code-backgrounds

Add github-style backgrounds to code blocks