[bug 902108] Add dennis v0.3.7 to vendor/

This updates polib and adds dennis to vendor/. Now we can do things
like:

    ./manage.py lint
    ./manage.py translate

Also, this nixes poxx.py and localelinter.py which aren't needed
anymore.
[bug 902108] Add compile-linted-mo.sh script
[bug 902108] Fix deploy script to run compile-linted-mo.sh