The HTML parser has been completely replaced. The new HTML parser is built on Python's html.parser.HTMLParser, which alleviates various bugs and simplifies maintenance of the code.

The md_in_html extension has been rebuilt on the new HTML Parser, which drastically simplifies it. Note that raw HTML elements with a markdown attribute defined are now converted to ElementTree Elements and are rendered by the serializer. Various bugs have been fixed.

Link reference parsing, abbreviation reference parsing and footnote reference parsing has all been moved from preprocessors to blockprocessors, which allows them to be nested within other block level elements. Specifically, this change was necessary to maintain the current behavior in the rebuilt md_in_html extension. A few random edge-case bugs (see the included tests) were resolved in the process.

Closes #595, closes #780, closes #830 and closes #1012.

Ignore empty braces. Braces must contain at least one non-whitepsace
character to be recognized as an attr list.

Attr lists for table cells must be at the end of the cell content and must
be seperated from the content by at least one space. This appears to be
a breaking change. However, it is consistent with the behavior elsewhere.

Fixes #898.

* Add `language-` prefix to output when syntax highlighting is
  disabled for both codehilite and fenced_code extensions.
* Add `lang_prefix` config option to customize the prefix.
* Add a 'pygments' env to tox which runs the tests with Pygments
  installed. Pygments is locked to a specific version in the env.
* Updated codehilite to accept any Pygments options.
* Refactor fenced code attributes.
   - ID attr is defined on `pre` tag.
    - Add support for attr_list extension, which allows setting arbitrary 
      attributes. 
    - When syntax highlighting is enabled, any pygments options can
       be defined per block in the attr list.
    - For backward compatibility, continue to support `hi_lines` outside
      of an attr_list. That is the only attr other than lang which is allowed
      without the brackets (`{}`) of an attr list. Note that if the brackets
      exist, then everything, including lang and hl_lines, must be within
      them.
* Resolves #775. Resolves #334. Addresses #652.

Add a config to set the footnote separator. Also remove rel/rev as they aren't really compatible with HTML5 and we already have classes set for refs and backrefs.

Fixes 723.

This was adapted from 11408e50 of the md3 branch.

Additional CSS classes names can be appended to the admonition name
using spaces as separators.

The following markdown:

    !!! note floatright
        This is a floating note.

Generates the following HTML code:

    <div class="admonition note floatright">
        <p class="admonition-title">Note</p>
        <p>This is a floating note.</p>
    </div>

All file-based tests are now defined as unittest test cases via a
metaclass which walks a directory and builds a unittest for each pair
of test files.

To run the tests just run `python -m unittest discover tests`. Or use
tox as the tox config has been updated to run the new tests and all nose
specific code has been removed.

The test generator tools have been removed as well. If any changes or
additions need to be made to tests, they should be implemented using
the new framework rather than with the file-based tests. Eventually,
only the PHP and pl tests should remain as file-based tests.

Preserve the line which a reference was on to prevent raw HTML indexing issue. Fixes #584.

Prevent raw HTML parsing issue in abbr and footnotes

Peserve abbreviation line when stripping and preserve a line for each footnote block.  Footnotes should also accumulate the extraneous padding.

Test extra lines at the end of references

Strip the gathered extraneous whitespace

When processing footnotes, we don't actually care to process the extra whitespace at the end of a footnote, but we want it to calculate lines to preserve.