Use Formspree instead of Brace Forms

From an email from Brace Forms:

> Brace.io is closing down, and Brace Forms has been open sourced. You have the option to move to formspree.io, a new service based on the open sourced code and hosted by Assembly.com. Check it out at http://assembly.com/formspree. Alternatively you can host your forms using your own server.
> 
> WHAT YOU SHOULD DO:
>
> You must change your form URL to formspree.io, or your own hosting, and re-confirm by January 19th. To do this:
> 
> 1. Change the action URL on your form from "http://forms.brace.io/your@email.com" to "http://formspree.io/your@email.com", or use your own server. Instructions for self hosting can be found at http://github.com/braceio/forms.
>
> 2. Submit the form once, and click "confirm" in the generated confirmation email.
Merge pull request #104 from TimothyGu/patch-1

Use Formspree instead of Brace Forms