Fix StorageGlobber test suite errors on  Windows

The StorageGlobber tests were failing on windows
because the paths get normalized to use two slashed by os.path.join.
Fixed by normalizing all paths in StorageGlobber and changing
expected results in the tests to use the normalized form.
Merge pull request #39 from randlet/fix-windows-tests

Fix StorageGlobber test suite errors on  Windows