restrict version of database cleaner

Author: elspethsoup

rubycas-client.gemspec

@@ -24,7 +24,7 @@ Gem::Specification.new do |gem|
 
   gem.add_dependency("activesupport")
   gem.add_development_dependency("rake")
-  gem.add_development_dependency("database_cleaner")
+  gem.add_development_dependency("database_cleaner", "~> 0.9.1")
   gem.add_development_dependency("json")
   gem.add_development_dependency("rspec")
   gem.add_development_dependency("appraisal")