support non-ASCII characters in usernames

[salim-b]

If I try to run gitdriver, it fails with the following error:

Traceback (most recent call last):
  File "gitdrive.py", line 114, in <module>
    main()
  File "gitdrive.py", line 112, in main
    commit_revision(gd, opts, rev)
  File "gitdrive.py", line 68, in commit_revision
    rev['lastModifyingUserName'])], env=env)
UnicodeEncodeError: 'ascii' codec can't encode character u'\xfc' in position 8: ordinal not in range(128)

If I'm understanding it right, this is because my Google username (lastModifyingUserName) includes the character ü. Would be nice if non-ASCII characters could be supported.

[larsks]

Thanks for the report! While I probably won't be able to get to this anytime soon, I am happy to accept pull requests.