Update AA version dependency

Author: dkniffin

activeadmin_dynamic_fields.gemspec

@@ -15,5 +15,5 @@ Gem::Specification.new do |spec|
   spec.files         = `git ls-files -z`.split("\x0")
   spec.require_paths = ['lib']
 
-  spec.add_runtime_dependency 'activeadmin', '~> 1.0'
+  spec.add_runtime_dependency 'activeadmin', '>= 1.0'
 end