Determining if you are using a release candidate

[alexpyoung]

Currently a user cannot determine if he/she is using release candidate version of Dusty. dusty version and dusty -v truncate this information and only display the semver release number. Given that users can install release candidates through dusty upgrade, I think it makes sense to provide confirmation in some form. The easiest solution in my mind is to communicate this in dusty -v. For example, if a user upgrades to 0.7.1-RC5, dusty -v will output

Dusty version 0.7.1

It could instead output

Dusty version 0.7.1-RC5