Add config prompt design inspired by bower and npm

Note: the original PR (#207) was botched - this is my second attempt.

---------------------

Very simple update (no changes to code execution) and therefor no added tests.

Simply a cleaner config prompt, inspired by bower and npm.

Before: ``full_name (default is "Your full name")?``
After: ``[?] full_name: (Your full name)``

/cc @michaeljoseph