Merge pull request #4 from TroyOfHelen/master

fix homework 1 question 1, minus sign and concept
test
Fixed the lecture image stuff
Tried to fix the pdf conversion
completing the merge
hw4 added
Fixing the pdf issues
Converting pdfs
Still figuring out the pdf thing
Think that I have it figured out
Converting more pdfs
Added names lectures
Added a utility function for copying files
Added some asset files
Converted lecture 02_01 from portrait to landscape
Merge branch 'master' of github.com:bcaffo/courses
Provided linked pdfs for data science
Don't know why rCharts wasn't rendering
Could not get js rendering to work
Merge branch 'master' of github.com:bcaffo/courses