Start to email invitations

I have setup a Mandrill account so we can send emails when invitations are posted. Also started on actually processing the link click, but that is just starting.

Also, more related to you guys, now there is Procfile-dev for use with the tool foreman (https://github.com/ddollar/foreman). Run 'foreman start -f Procfile-dev -p 3000' and as long as nodemon is installed foreman will run AgreeMates with any configuration settings inside of .env . That file is git-ignored, so you will need to create it on your own system and fill it in with any necessary config settings (check Heroku for ones that we will be using in the main app such as Mandrill and various database settings). Just put them on newlines like such:

```
MANDRILL_USER=SDLFJKSLDF
MANDRILL_PASS=SDLKasdfSDLKJfadsf
```