I think that Pathname doesn't consider paths starting with the `~` absolute as they are not exactly absolute:

For example the following `~/Docs` resolves to `Users/fabio/Docs` in my system and will resolve to `Users/NAME/Docs` in another. However from our point of view, that is an absolute path (maybe we should use `relative` and `non_relative` to the installation dir).

I would prefer to use [`File::expand_path`](http://ruby-doc.org/core-1.8.7/File.html#method-c-expand_path) as early as possible while handling the files of the Podfile... that should ensure that Pathname and the other methods properly identify `relative_paths`.