SSL checkbox to popup & additional encrypt option

Fixes authentication to some TLS SMTP servers (Issue #46) by facilitatating the ability to set different encryption types. Current options are None, SSL/TLS, and StartTLS.
![screen shot 2014-07-16 at 1 43 10 am](https://cloud.githubusercontent.com/assets/945258/3595035/83d3b080-0cad-11e4-93e8-9eb3f8506c3d.png)
Dropdown options: 
![screen shot 2014-07-16 at 1 54 39 am](https://cloud.githubusercontent.com/assets/945258/3595044/bf4489d2-0cad-11e4-9fe7-3051e6e4e005.png)