Add a function to convert location data to filemaps
Modified dependency code to handle custom location

The code was modified so now we can provide custom locations for modules
in the form of a dictionary like object mapping object name to its
folder.
Split tests in various files
Add filemap support to open package
Forgot a single filemap change
Dependencies of dependencies were not handled correctly
Remove ugly hack for dependency location
Merge pull request #11 from antoinealb/master

Properly implement dependency directory selection