Code review comment for lp:~sneakypete81/zim/pyzim

Solves problem under Windows where file:///c:/path/to/file was appearing as /c:/path/to/file and then c:\c:\path\to\file, since the lower-case drive letter was not detected.

This problem meant Zim failed to find existing notebooks.

Hope I've done this properly, I'm a launchpad beginner..