Allow ActiveAdmin 3

Author: alejandroperea

activeadmin_quill_editor.gemspec

@@ -25,7 +25,7 @@ Gem::Specification.new do |spec|
   spec.files         = Dir['{app,lib}/**/*', 'LICENSE.txt', 'Rakefile', 'README.md']
   spec.require_paths = ['lib']
 
-  spec.add_runtime_dependency 'activeadmin', '~> 2.0'
+  spec.add_runtime_dependency 'activeadmin', '>= 2.0, < 4'
 
   spec.add_development_dependency 'appraisal', '~> 2.4'
 end