Get git install woking

@futureimperfect , not sure if you had this working and disabled it, but here's my novel approach.
1) Launches xcode-select --install. 
2) Back in AutoPkgr waits for user to click OK after "Command Line Tools" install completes
3) If it still isn't installed, shows an alert that redirects them to the http://git-scm.com/downloads.

Still would be nice to get it downloading directly from source forge, but at least it will work and somewhat addresses #61.