Fixes #1845 - Default assets registered twice by ActiveAdmin.setup

[michaelrshannon]

Implements changes suggested in issue #1845 comments

[macfanatic]

Will you please add a spec for this in spec/unit/asset_registration_spec.rb?

[exviva]

Cool! This is related: ejholmes/active_admin_editor#20

[seanlinsley]

Our Travis builds on master are now green (as of 166bc46). Please rebase your PR on the current master:

# Expectations: "upstream" is gregbell's GitHub repo and "origin" is your fork

# Rebase your fork's master branch with the latest upstream changes
git checkout master
git pull --rebase upstream master
git push origin master

# Rebase your feature branch with the latest upstream changes
git checkout your_feature_branch
git pull --rebase upstream master
git push origin your_feature_branch # note that you may need to use -f

[seanlinsley]

Ping @michaelrshannon; this still needs tests!

[michaelrshannon]

Thanks - been away, will deal with this week.

[seanlinsley]

It's been two weeks now :P

[seanlinsley]

Closing this in favor of #2139