Enable support for comparing files provided the path is URI.

If I want to compare files on web, at first I had to download them manually and then compare them.
The same applies for FTP or other protocols.
If the file is located on local disk, then it would be fine to use "file" scheme.

Suppose I want to compare file on web and file on local disk:
- http://www.example.com/bower.json
- file:///C:/temp/bower.json