UTF-8 Key Attributes

They key parameters are expected to be UTF-8 strings according to the documentation[1]. 

- [ ]  Write a minimal test case for UTF-8 key parameters. 
- [ ] Figure out if it makes sense to set an encoding for the other strings.

[1] - http://www.gnupg.org/documentation/manuals/gpgme/Generating-Keys.html#Generating-Keys