An easy way to update propel from github

We were using svn:externals to keep Propel ORM (and other libs) up-to-date in our projects. (You should always have your libraries project-local).

I wanted to keep my development process lean and highly automated, that's why I wrote this bash-script to update Propel to the desired tag.

Hope it will be useful to others also (use at own risk..)

Niklas Närhinen