Tune up first advanced section on hashing
Merge remote-tracking branch 'origin/dark-ship-style-tuning' into section-headers
Bulleted lists become slides. Resource wording tuneup.
Videos and slides iframed-inline
Expand additional resources into slide chunks
Fleshed out refspecs
Merge pull request #208 from github/section-headers

Tune up opening slides to each module of class