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`
Windows, Virtualbox, and npm don't get along very well.  You can't make symlinks in a VirtualBox shared folder, and npm makes tons of symlinks.