Emails coming from the webapp frequently end in spam

[fltfx]

Problem

Email such as the RSVP emails that are sent out, and likely event the application confirmation email often end up in the recipient's spam folder.

Suggestions:

1. Upon the applicant submitting their application (the form), the message in the webapp (sorry, I didn't have time to dig into what exact message is shown or if there is a message shown) should mention something like:

Thanks for your application... (blah blah). Our emails have a tendency to end up in spam, so please look in your inbox for a confirmation email that we have received your application (check your spam/junk folder!) and please add our email address (xx@djangogirls.org) as a saved contact, so our next emails won't end up in spam!

2. In the confirmation email, we repeat the message to add our email address to saved ones, so subsequent emails don't end up in spam. This should likely be the template that needs updating.
   templates/emails/organize/application_confirmation.html

[fltfx]

@kewtree1408 fyi :)