changing index file
reinstating two-column format
changing header levels
adding borders-background effect
adding wells
editing wells
redoing overview includes
stripped empty lines
hardcode Git Bash download to 1.8.4

1.8.5.2 is currently buggy, see
https://github.com/swcarpentry/bc/issues/234#issuecomment-32764692
Fix R installation links.

Suggested-by: Bernhard Konrad <konradbe@math.ubc.ca>
See: https://github.com/swcarpentry/bc/pull/211#issuecomment-33077628
Fix Mac OS X wordery to include 10.9

Suggested-by: Bernhard Konrad <konradbe@math.ubc.ca>
Merge pull request #259 from swcarpentry/ChristinaLK-fixes

ChristinaLK Suggested Fixes to Setup