Added ability to have deep partials. Now supports {{>sub-dir/partial}}.

Added ability to have subdirectories of partials.

Now docs can have a tree of:
docs -
- partials
  - exampleA
     - a-full.mustache
     - a-markup.mustache
     - a-style.mustache
  - exampleB
     - b-full.mustache
     - b-markup.mustache
     - b-style.mustache

You would use exampleA's full mustache partial with {{>exampleA/a-full}}

This promotes a more modular approach to partials and example support files.