Cleaned up URL generation code for toclabel
Modified handling of edXxml to remove spaces after ampersand and dollar sign introduced by plasTeX, and handled text and tail content
Added \index plasTeX functionality to render files and main.py to generate a key_map.json for use with a searchable index
Merge pull request #12 from evheubel/master

Modified edXxml behavior for special character handling, and maintaining text/tail content.