Merge pull request #117 from d0ugal/master

Add building docs as an integration test
Configurable Markdown extensions

This lets the YAML configuration specify a list of Python Markdown extensions
to enable (on top of the default set). This is especially handy, for example,
when you want nice typography via the SmartyPants extension.
Add docs for markdown_extensions
Fix crash when markdown_extensions is not set

This lets the value be a tuple as well as a list. (Never really understood why
Python won't concatenate lists and tuples.)
Add test for extension enabling

I didn't use the SmartyPants extension here because the version of
python-markdown pinned here (2.3.1) doesn't include the extension. 2.4 does;
maybe the project should consider updating this dependency.
Add test for duplicated custom extension names
Fix comment copypasta error
Test against py33 and py34
Add python 2/3 compatibility module
Fix urlparse py2/3 compatiblity in build.py and config.py
Fix all py3 syntax errors; All tests passing
Minor style fixes as per @tomchristie's code review
Fix ordering of imports as per the project's conventions

Always order imports alphabetically
Fix httpserver and socketserver compatibility with py3
Fix a few encoding errors
Fix unquote compatibility
Add future import; remove unnecssary lines in compat.py
Prevent ResourceWarning due to unclosed file
Updated docs/about/license.md with theme license links
Merge pull request #118 from rlabrecque/patch-1

Updated license.md with theme license links