Utilities.get_repository refactoring

`Utilities.get_repository` always bothered me. I don't generally like `while` loops in Ruby, so I promoted it to use the `Pathname.ascend` (see [docs](http://www.ruby-doc.org/stdlib-1.9.3/libdoc/pathname/rdoc/Pathname.html#method-i-ascend) for more info). 

Also, use `exit 0` with a simple `puts` for informing the user of the error instead of a straight `raise`. Looks nicer :wink: 

If you feel it's a little too tricky, I'll refactor for a bit more clarity and squash my commits...