intro to git lectures now separated by mac and windows install
Merge pull request #74 from rdpeng/master

Added lecture on coding standards
split creating a repo lectures into two pieces - one for creating repo from scratch and another for forking a repo
Merge remote-tracking branch 'upstream/master'
Merge pull request #75 from rdpeng/master

Coding standards lecture
Merge pull request #76 from ncarchedi/master

git and github lecture updates