Initial hieroglyph slides

This configuration does a few things:

* Default html build does not build anything under ``slides`` (based on the ``excludes_patterns`` config in ``conf.py``. Since I'm changing the buildroot of the slides make command, it also includes anything under that when you build slides too.
* Builds slides as a slides sub directory of the content

**NOTE: I had to make a separate doctree directory for each build otherwise sphinx would complain.**
As discussed on IRC, we'll finalize this point later.