This reverts commit 72461609.

The headers were pointing to the old github wiki. Since we've officially
moved to Confluence, these links should be updated.

Also support updating repositories such as python graders
from xqwatcher/xserver

This modifies the edx_ansible role to dump a clean var
file on disk that can be used for subsequent update runs
so that config vars will not be lost

also changes the ansible tmp directory to /var/tmp which is a better
location than using $HOME (used for debugging mostly)