Fix redirect handling and case sensitivity

* treat #REDIRECT as case-insensitive
* make the first letter in Category and Disambig pages case-insensitive
	see:
	   http://en.wikipedia.org/wiki/Wikipedia:Manual_of_Style/Linking
	   "However, links are case-sensitive for all but the initial character."

	   http://en.wikipedia.org/wiki/Help:Template
	   "Template names are exactly like other page names: case-sensitive except for the first letter"
* recognize both the {{disambig}} and {{disambiguation}} disambiguation templates
* add `redirect_page` field

Closes #14.