Fix a typo
Merge remote-tracking branch 'origin/master'

* origin/master:
  Remove ridiculous hack needed to get S4 to work in slidify
  Don't track PDF version of slides
Start the process of creating new directories for using dev version of slidify
Libraries directory from dev slidify
Copy over old CSS file to preserve look
Move loading/installing packages to new dev directory
Revise paths to libraries/assets
Fix paths to images
Merge pull request #13 from rdpeng/reorg

Reorg of roger's lectures to deal with showing methods/classes in his lecture