Email alert that BBNB is running and updated

[jtschulz]

This email should include short explanation of why we closed (site was more popular than we had planned for and our email strategy didn't scale) and what we changed (daily emails vs every time, added FAQ) with thank you and apology for inconvenience.

[jasnow]

Moved this line from #317: "We will also email all active users about the new changes."

[jasnow]

Received and reviewed draft email.

[jasnow]

Here is the draft text from @PepperTeasdale :
https://gist.github.com/jasnow/a0929c8c46df3f9f1e680b25d61b9de5