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`
.... Actually, I just reprovisioned and it stopped working again.  I think I want this to be `0774`.  Will make sure to reprovision and retest.