Update constructor to handle parent changes.

Previously there was no constructor for the `ExampleGroup`. This changed
with rspec/rspec-core#1687. Instead of exactly matching the contructor,
use the standard Ruby argument catch-all to simply delegate up the
chain.

lib/rspec/rails/adapters.rb

@@ -121,7 +121,8 @@ def teardown(*methods)
         end
       end
 
-      def initialize
+      def initialize(*args)
+        super
         @example = nil
       end