Merge pull request #8 from ncarchedi/master

put all content into folders based on data science curriculum
Start loading/installing packages lecture
Added toolbox lecture, hopefully just to jeff
Talk about CRAN/Bioconductor; basic install
Rename lecture directory
Screenshots for Load/Install pkgs in RStudio
started on data science toolbox
Cropped screenshot
Rename image
Resize image
Using install.packages
toolBox almost done
Draft lecture slides
Talk about search list and compute number of packages
Shorten Bioconductor reference
Merge pull request #9 from rdpeng/loadpkg

Installing and Loading Packages
Run code dynamically
Don't track html and md files
Add cachemean example
Fix some typos; adjustments