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 think not using `ENV.fetch` here could cause issues with Jenkins. While you're here, the port forwarding definition above it should probably use `ENV.fetch` too.