Email logging

[xet7]

Moved to here from phildini#39

From @oboechick

Once I have sent an email, I would like to be able to see if the email that I have sent (and have logged as being sent) has opened the email.

From @phildini

This could be another mailchimp integration thing, or contactotter could have it's own open pixel.

@oboechick, do you think this should be in the log line for sending the email?

From @oboechick

I think it would be nice to know if what I sent arrived but only if I were to use this for large groups of people. On a personal level it matters less to me.