Register Comment as AdminComment

Fixes gregbell/active_admin#301.
Resolves #587 adding :if & :unless proc arguments to scope_to() method
Merge pull request #2015 from Daxter/refactor/cucumber_step_definitions

Cucumber cleanup
Merge pull request #2060 from jbhannah/register-admin-comments

Register Comment as AdminComment
Merge pull request #2089 from macfanatic/scope-to-conditional-display

`scope_to` now accepts :if / :unless arguments
add better_errors to improve debugging experience
Merge pull request #2095 from Daxter/dev/add_better_errors

add better_errors to improve debugging experience
make ResourceCollection behave more like a Hash

unneeded complexity is unneeded