Replace exception used for flow control with idiomatic throw/catch.
Refactored conditional to an || to be more idiomatic.
Refactor select().map() to use pluck.
Remove a method already provided by ActiveRecord.
Various idiomatic User refactorings.
Merge pull request #871 from avdi/refactoring-with-josh-and-avdi

Various refactorings towards Ruby/Rails idiom from Josh Susser and Avdi Grimm