temporary update script

Until we get proper software updates working we need a script we can run
to orchestrate installs -- checkouts, collectstatic, restarts.  Tagged
with the "update" tag.  Just puts the file out there for now, doesn't
actually do any updates, that should be done with something like this:
    ansible GROUPNAME -i ./ec2.py -c ssh -s -a edx-update.sh
use git fetch origin instead of remote update, more correct
Merge pull request #56 from edx/feature/sef/software-update-script

temporary software update script