rails4 compability
Update active_admin-awesome_nested_set.gemspec

Try Rails 4.0
Allow both old and new rails
Allow both old and new rails
Merge branch 'master' of https://github.com/aderyabin/active_admin-awesome_nested_set into aderyabin-master

Conflicts:
	active_admin-awesome_nested_set.gemspec
Bumped version to 0.0.6
Merge pull request #3 from sandfox-im/master

Rails 4.0 compatibility