Add email functionality as input

In an older version of the code we had the option to send an email when the code hit a certain step (as in, to tell someone to go change move/change something after a 'stop' command or when the run is done or something). It would be nice to have this again. This would probably be implement just by adding an "email" input option (as opposed to transfer/make/plot/dilute/etc) and we could either include the email as an input or hardcode the email address in (let's discuss before choosing which route to go).