HTML5 doctype, Wrap TOC with <nav>

<nav> makes the TOC more easily identifiable and workable with CSS.
Add some HTML5
Merge pull request #15 from moshee/master

HTML5
Fix up method documentation formatting.
Fix html tag ordering in doc string.
Merge pull request #16 from cespare/blockcodegithub_doc_fix

Fix up method documentation formatting for the BlockCodeGithub method.
Make a way to parameterize inline tests

Expose extensions and html flags parameters so that tests could specify
what code paths they want to exercise.
Fix bug in isHtmlTag()

Fix what seems to be a typo. j should iterate through all tagname, so it
should be initialized to zero. The test exposes this bug.
Extract repetitive code to a func
Make isHtmlTag() case insensitive
Add an option to strip <script> elements

Partially addresses issue #11.
More <script> stripping

Partially addresses issue #11.
Couple more tests
Add HTML_SKIP_SCRIPT to MarkdownCommon
Fix typo
Improve html element stripping code
fix table syntax example
Merge pull request #24 from subosito/sample-fixes

Fix table syntax example on README
Merge pull request #22 from rtfb/master

Add some protection against script injection
First attempt at supporting Pandoc-style footnotes. The existing tests have not broken but the new functionality does not work yet.