Remove database-cleaner.

- It was not able to work with mongoid 5
- I don't see the reason to use both Mongoid.purge! and
  DatabaseCleaner.truncate! It looks like doing double work

mongoid-enum.gemspec

@@ -24,6 +24,5 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "rake"
   spec.add_development_dependency "rspec", "~> 3.1"
   spec.add_development_dependency "guard-rspec", "~> 4.6.2"
-  spec.add_development_dependency "database_cleaner", "~> 1.2.0"
   spec.add_development_dependency "mongoid-rspec", "~> 3.0"
 end

spec/spec_helper.rb

@@ -1,20 +1,15 @@
 $: << File.expand_path("../../lib", __FILE__)
 
-require 'database_cleaner'
 require 'mongoid'
-require 'mongoid-rspec'
+require "mongoid/rspec"
 require 'mongoid/enum'
 
 ENV['MONGOID_ENV'] = "test"
 
 RSpec.configure do |config|
   config.include Mongoid::Matchers
-  config.before(:suite) do
-    DatabaseCleaner.strategy = :truncation
-  end
 
-  config.after(:each) do
-    DatabaseCleaner.clean
+  config.before(:each) do
     Mongoid.purge!
   end
 end