Mo heroku support

This completes the basic heroku deployment support.  The bugfix is the minor change to session.js, the other file is the config template.  Here is the useful info on getting this to work on heroku:

Heroku instructions.
---

1. create an app (**heroku apps:create snorkelista**, for example)
2. set environment variables on heroku for the app:
   1. heroku config:add MONGOHQ_URL=mongodb://user:pwd@host:port/db
   2. heroku config:add ENV=heroku.js
   3. heroku config:add HTTPHOST=snorkelista.herokuapp.com (or whatever you use)
   4. heroku config:add GPLUS_DOMAIN=yourcompanydomain.com (or change heroku.js to configure auth)
3. push everything under the snorkel directory (in particular the Procfile) to your heroku git repo.

The app should be working now.

---
**Note**:  you can get a hosted mongodb via various mongo addons (**heroku addons:add mongohq -a snorkelista**, for example)
**Note-2**: the default config does not lock down the snorkel API which it probably should if used in any serious production environment.