Cleaner config prompt inspired by bower

Very simple update (no changes to code execution) and therefor no added tests.

Simply suggests a *cleaner* config prompt, inspired by [bower](http://bower.io/) and [npm](https://www.npmjs.org/).

- Before: ``full_name (default is "Your full name")? ``
- After: ``[?] full_name: (Your full name) ``

Not fixing any current issues (that I know of :smile:) but relates to #173 - could be a prior step to adding additional features.