Integrate proof of concept gulpfile into Django project

 - Changes the Django `static` and `media` directories to be inside `/var/www/nyc-trees/`
 - Adds the `static` template filter for converting static file to use their versioned path
 - Fixes a few issues with the proof of concept `gulpfile`
I can switch to that.  For things that are only really useful for development though (I don't think anyone will be live-reloading production), what about just adding `auto_correct: true`?