Typo.
Merge pull request #44 from eggrobin/2e4ace22f3e6143d3315282f843fe28f591138da

Fixed a typo in the wrong branch, and it's going to be a while before lecture-2013-03-28 gets merged into master.
Catch up.
Fixed some layout issues.
Merge pull request #46 from eggrobin/lecture-2013-03-16

Lecture 2013 03 16