Boomerang : Email myself

# The second email is now a paid feature.

As Boomerang welcomes more and more users, the maintenance of the app has become costly. To sustain development, I have decided to make the second email address feature a paid option. It's a one-time payment; I hope it's affordable for everyone. Please share your feedback using the form inside the app. Thanks for your support!

+ Fix bugs and improve performance.

Thanks for using Boomerang,
Thomas.