refactoring and simplifying

eliminate template customization for search results
add “label” to DSL to specify a method or block for each model that
generates text for use in search results (or elsewhere)
fallback to “model_label” at the top level of the config for a list of
methods that will be checked in order to find a label
factor out Presenter for JSON config
factor out Search for search config
set up RSpec (without Rails! wooo)
write some specs for config and Presenter