Added SendGrid. 

- SendGrid is working with the letter opener gem. 
- I added a couple of chores to the seed data
- SendGrid required me to sign up for a free account and I used my own info, but the password is included in the application.yml file. You shouldn't actually need it, but if you do, you can see it there. 
- SendGrid takes a bit to verify your account, so real mail won't work yet.