Remove explicit return from ensure clause

* There is a subtle difference in functionality, but it doesn't affect
  the implementation here.
* See #14 (comment)
  for more information.

[#14]

Author: iamvery

spec/support/capture_stdout.rb

@@ -5,7 +5,7 @@ def capture_stdout
   real_stdout = $stdout
   $stdout = captured_output
   yield
+  captured_output.string
 ensure
   $stdout = real_stdout
-  return captured_output.string
 end