added intro to git and intro to github lectures plus associated images in assets folder
Merge pull request #18 from ncarchedi/master

intro to git and intro to github lectures
added create repo lecture and images
Merge pull request #19 from ncarchedi/master

added create repo lecture and images
added rtools lecture - has user install devtools as well
added CLI lecture
Merge remote-tracking branch 'jtleek/master'
fixed a typo
Merge pull request #21 from seankross/master

added CLI lecture
Merge pull request #20 from ncarchedi/master

added rtools lecture - has user install devtools as well
Merge remote-tracking branch 'origin/master'

* origin/master:
  fixed a typo
  added CLI lecture
  added rtools lecture - has user install devtools as well
  added create repo lecture and images
  added intro to git and intro to github lectures plus associated images in assets folder