added basic toemail block

I've created a simple toEmail block. 

The rules expect a host, port, user and pw for smtp (defaults to Gmail's host & port) and it also expects a to, from and subject for the email messages it will be sending.

When the block receives a message, it json.Marshal's the message into the body of the email and sends it with the given creds, to, from and subject.

It's pretty easy to hook it into the wiki edits example and spam yourself. I'll send you an export with a junker email address in it if you're interested.