swap connection check with ORM check first to make it Mongoid compatible

connected? method doesn't exist in Mongoid
refs RolifyCommunity#222

lib/rolify/configure.rb

@@ -45,12 +45,16 @@ def sanity_check(role_cnames)
       role_cnames = [ "Role" ] if role_cnames.empty?
       role_cnames.each do |role_cname|
         role_class = role_cname.constantize
-        if role_class.connected? && role_class.superclass.to_s == "ActiveRecord::Base" && !role_class.table_exists?
+        if role_class.superclass.to_s == "ActiveRecord::Base" && role_table_missing?(role_class)
           warn "[WARN] table '#{role_cname}' doesn't exist. Did you run the migration ? Ignoring rolify config."
           return false
         end
       end
       true
     end
+
+    def role_table_missing?(role_class)
+      role_class.connected? && !role_class.table_exists?
+    end
   end
 end