Add a rake task to setup DATABASE_URL for ClearDB

There currently is no other way to inherit environment
variables from parent apps on heroku

lib/tasks/cleardb.rake

@@ -0,0 +1,11 @@
+namespace :db do
+  desc 'setup DATABASE_URL from CLEARDB_DATABASE_URL in .env'
+  task cleardb_env: :environment do
+    unless ENV['CLEARDB_DATABASE_URL'].nil?
+      cleardb_url = ENV['CLEARDB_DATABASE_URL'].gsub(/^mysql:\/\//, 'mysql2://')
+      dot_env = File.open(Rails.root.join(".env"), 'w')
+      dot_env.puts "DATABASE_URL=\"#{cleardb_url}\""
+      dot_env.close
+    end
+  end
+end