oops, don't raise an exception!
simplify options handling code for `actions`
style update
make `default_actions` private

note: this is a backwards-incompatible change!
changed spec syntax from should to expect
Merge pull request #3136 from irmiller22/rspec-syntax-change

RSpec Syntax Change
use expect() RSpec syntax in Cucumber steps
simplify ActiveAdmin::BatchActions::BatchActionPopover#action
Merge pull request #3139 from timoschilling/code_simplification

simplify ActiveAdmin::BatchActions::BatchActionPopover#action