Use viper to read api keys from config file instead of taking at compile time

[mattgen88]

Use viper to read api keys from config file instead of taking at compile time
if no config file exists, scrobble should prompt user for them or direct user to set them, possibly creating skeleton config file.
Scrobble could use the same mechanism to also take them from environment.

[mattgen88]

Scratch that, they need to be stored in the released binary. Closing.