added sendgrid and ENV variables. modified devise views and welcome view...

Per the instructions in [Finish Devise](https://www.bloc.io/users/joe-palmieri/checkpoints/670) checkpoint.

I modified the views to include bootstrap classes, although I haven't added bootstrap yet. I plan to add bootstrap in the next pull request.

I only added sendgrid to development right now (per the instructions). One thing I noticed was that the confirmation email took a REALLY long time (maybe 10 minutes or more) to arrive. I tried to resend it a few times more, and they all seemed to arrive, but about 10 minutes after I requested them. Do you think this is because of my configuration or maybe because of Sendgrid traffic?