Added slides

Added the keynote presentation and a PDF version
Initial commit
astroML capter 2 ipnb
Merge pull request #1 from ih64/master

@ih64 @abonaca Got it!
added a ipython notebook about trees
Merge pull request #2 from duncandc/master

added a ipython notebook about trees
edits and typos fixed
Merge pull request #3 from ih64/master

edits and typos fixed
stuf
moved ch2 to directory
removed old README
data visualization
use default data repository
moved all to Session1
Merge branch 'ch1'
Merge branch 'ch2'
moved session3 items to directory
update README
removed .ipynb_checkpoints and added to .gitignore
session4