Switch to generating HTML ourselves, without the help of any XML/HTML library.
Changes required to support removing nokogiri dependency from math modules.
Rework blahtex support to no longer use Nokogiri or PStore cache.

The blahtex support code has been simplified to no longer cache mathml in an unbounded file-based cache, and it no longer writes tempfiles. The extremely simple XML parsing job has been handed back over to REXML.
Remove explicit Nokogiri dependency for itex2mml module.
Fix TOC generation to match older Maruku.

Maruku 0.6.1 would notice if a single header encompassed the entire document, and would make that the root section of the document, as well as setting the title to that header's content. This restores that functionality.
Remove Nokogiri dependency from the S5 slides output.

This change switches to using the HTML output utilities to generate S5 slides. It also restores the STDOUT printing of slide titles
that current Maruku does, but only from the CLI (it won't annoy users who programmatically generate slides).
Switch to parsing XML/HTML fragments using a wrapper document that includes a doctype.

This preserves both the case of attributes and any named entity references from MathML.
Return to obfuscating emails with character entities.