gollum-lib changes required to implement per-page uploads
Merge pull request #49 from anchor/per-page-uploads

gollum-lib changes required to implement per-page uploads
Convert the markup class to use "filter chains"

Refactor out the steps required to turn a marked-up file into a HTML
fragment ready for display into individual classes.  The benefit of this is
that users can modify the processing chain for their own needs, without
needing to go subclassing Gollup::Markup.  This should be a big win.

It's a conceptually simple change that gets a bit messy, since the
extraction and processing code got its tentacles into a few places.

In essence, each phase of rendering a page is encapsulated in a separate
class with extract/process methods, more-or-less mirroring the existing
structure.  I had to take a bit of a gamble between sharing state between
filter steps (via the markup class instance) and redoing some things
multiple times (HTML parsing/assembly), but I felt that was cleaner than the
alternatives, especially since if we store a parsed document, we'd have to
make sure that cache wasn't invalidated by an intermediate step.
Merge pull request #50 from anchor/render-chain

Convert the markup class to use "filter chains"
Remove duplicate rake
Merge pull request #52 from anchor/duplicate-rake

Remove duplicate rake
Replaced Pygments with Rouge. See issue https://github.com/gollum/gollum-lib/issues/41
Merge pull request #53 from repotag/from_pygments_to_rouge

Replaced Pygments with Rouge. See issue https://github.com/gollum/gollum-lib/issues/41
Support Ruby 2.1.0. Closes #54
Gollum::Markup.formats now adheres to formatter limitations from config.rb (with tests). Fixes issue https://github.com/gollum/gollum/issues/771.
Merge pull request #56 from repotag/limit_formatters

Makes Gollum adhere to formatter limitations set in config.rb. Resolves issue https://github.com/gollum/gollum/issues/771 .
Added PlainText filter to render .txt files in <pre></pre> block without additional markup (with tests). Resolves https://github.com/gollum/gollum/issues/775 .
Merge pull request #55 from repotag/plain_text_formatter

Added PlainText filter to render .txt files in <pre></pre> block without additional markup (issue https://github.com/gollum/gollum/issues/775).
Allow [[include:]] directive to specify relative and subpage paths.  Fixes gollum/gollum#765.