Implement end-to-end encryption

[EionRobb]

End-to-end encryption is a thing. https://blog.pushbullet.com/2015/08/11/end-to-end-encryption/

Useful links to help implement: https://www.pushbullet.com/#settings/encryption https://docs.pushbullet.com/#end-to-end-encryption http://stackoverflow.com/questions/32259074/invalidtag-error-decrypting-pushbullet-notification-with-python-cryptography