Various Improvements

* Quick fix of Unicode issue and pep8.
* Made 'diff' 'show' instead; does a better job of showing you something worth looking at.
* 'checkout' no longer uses git-review and takes an optional patchset # so you can checkout older patchsets
* Added 'diffsince' which is awesome, if I say so myself: git fgerrit `<id>` checkout ; git fgerrit `<id>` diffsince `<last-patchset#>`

Try:
    export GIT_PAGER='vim -R -'