Add test for syncing packages with a non-default prefix

This test currently fails because of a bug.

In reference to #33.
Correct logic in package prefix test

In reference to #33.
Add Alexandre Viau to list of authors

Thanks for the contributions!  They are much appreciated.
Merge branch 'master' of https://github.com/jbernard/dotfiles
fix indent : tab to spaces
fix #33: syncing packages with prefix set