Make finder auth configurable

Updated the finder to support configurable auth modules, including a default RS auth module.
And to force retry auth on 401's.
Updated tests to excercise the new functionality, as well as add a test for the auth expiration function.
Refactored extraneous camelCase to snake_case

Note this code was reviewed and +1'd here:
https://github.com/gdusbabek/blueflood/pull/2

I'm just rebasing it into master.