Method calls with expanded arrays require parentheses

This fixes the following warning:

    lib/rspec/mocks/message_expectation.rb:43: warning: `*' interpreted
    as argument prefix

- Closes rspec#30.

lib/rspec/mocks/message_expectation.rb

@@ -40,7 +40,7 @@ def build_child(expected_from, method_block, expected_received_count, opts={})
         new_gen = error_generator.clone
         new_gen.opts = opts
         child.error_generator = new_gen
-        child.clone_args_to_yield *@args_to_yield
+        child.clone_args_to_yield(*@args_to_yield)
         child
       end