Add config for heroku

### What is the problem / feature ?

The volunteer database needed to be hosted on heroku.

### How did it get fixed / implemented ?

Made initial configuration changes to make that possible.

- Added `django-herokuify` and some other bits to the requirements.
- Added `volunteer/settings_heroku.py to handle heroku specific configuration that should stay out of the primary settings.
- Added an Amazon S3 user and bucket for serving of static files for the app.

### How can someone test / see it ?

visit http://voldb.herokuapp.com/

*Here is a cute baby animal picture for your troubles...*

![cute_dog_hugging_goat](https://f.cloud.github.com/assets/824194/2420584/1b16bdfc-ab74-11e3-8f93-5ab4181691bb.jpg)