Initial codebase

I'm committing this as a work in progress. If anyone has any suggestions or feedback, it's welcome!

TODO:

- [x] Render image as base64
- [x] Gather extra data (subject, domain from)
- [x] Output JSON with some extra data and the base64 image
- [ ] Create config loader for base path, destination url etc.
- [x] Make sure Gmail forwarding formatting is removed properly
- [ ] See what formatting other clients add (Mail.app, etc.)
- [ ] Make sure the app is deployable on Heroku
- [ ] Make sure all types of images are properly rendered by PhantomJS