add set difference exercise
updated exercise to make more sense, and hopefully be more interesting
Adding images to setup instructions
Splitting assertions from unit testing/TDD
Make the opening a little less scary
Suspected typo but not sure? bootcamp_slug? Otherwise just renders the command as `cd`
Merge pull request #34 from beroe/patch-1

Suspected typo but not sure? bootcamp_slug? Otherwise just renders the c...
replace richie with hopper
Adding outline for DLA exercise, and renaming other files to make room for more
Updating index page
Correct variable name.
Merge pull request #42 from douglatornell/fix-stack-image

Correct variable name in stack frame image.
Merge pull request #7 from tshauck/set-difference

Add set difference exercise
Merge pull request #37 from wltrimbl/hopperpicture

replaced richie.txt ascii art with ascii art of Dr. Grace Hopper
Merge pull request #33 from jessitron/gh-pages

Make the opening a little less scary
Growing a program (using a simpler example than invasion percolation)
Adding to the index
Merge branch 'gh-pages' of github.com:swcarpentry/bc into gh-pages
Starting NumPy lecture