Switch to HTML filetype

 - mustache files are still loaded
Better matchit support

 - matchit support for handlebars' if/else/if (unless included)
 - matchit support for mustache enumerators
Update syntax file

 - clean whitespace at the end of lines
 - added reference link for handlebars.js
 - changed mustache/handlebars markers to have `Special` syntax group
Update example.mustache

 - cleaned up end-of-line whitespace
 - added handlebars if/else/if example
Indicate mustache and handlebars support in readme
Merge pull request #11 from juvenn/updates

Merge in good additions from @bsutic