Allow nested parentheses in URLs
Markdown spoiler feature

As described here: http://meta.stackoverflow.com/questions/72877/whats-the-exact-syntax-for-spoiler-markup
Unify the -/= and ## style headers

so that TOC can be generated properly from a mixed-markup document.

With the current code the TOC for the following document:

````
hb
---
````

is generated as: hb ha hc, while the correct order would be ha hb hc
Process fenced code blocks before link definitions.
Fix fenced code blocks test that was wrong.
Add test for odd fenced code block case.
Rename to issue 135.
Issue 135.
Merge pull request #135 from nicholasserra/fenced-code-blocks-oddity

Fenced code blocks oddity
Fleshed out some contributor notes in the README.
Merge pull request #136 from trentm/dev/readme-fixes

Fleshed out some contributor notes in the README.
Update changelog for last PR.
Update contributors.
Merge remote-tracking branch 'upstream/master' into unify_header_handling
Retain existing unittest to avoid reducing coverage
Make makefile compatible with Ubuntu which uses sh as the default shell
Merge pull request #138 from udacity/makefile_compatibility_with_ubuntu

Make makefile compatible with Ubuntu which uses sh as the default shell
CHANGES
python 2.5 has been removed from travis-ci
Add break-on-newline option

This changeset adds the option for "break-on-newline" which adds a <br /> tag on each newline inside a paragraph. This makes the library behave more like [GitHubs markdown](http://github.github.com/github-flavored-markdown/).