Get mustache plugin working with new comment system

This commit has multiple fixes to get the mustache task working:

  - Update mustache.html to remove unused files/update versions

  - Remove disqus dependency and use the new comment system

  - Minor fix in template for the config file

Known issues:

  - We try to load custom.css even if none is defined.

  - raw.github.com urls are use for a couple of libraries.  These will
    soon stop working modern browsers. Ref: http://bit.ly/11E92ln
Merge pull request #631 from punchagan/fix-render-mustache

Get mustache plugin working with new comment system