Add support for mounting custom middleware in routes.

Hello @dpup, @azulus, 

Please review the following commits I made in branch 'vinny-middleware-support'.

To see how this feature works, please check the routes in the custom_middleware
app in the integration tests.

1efcf1e73f0128f504e034fd60eb55d6b6bdd152 (2013-05-22 13:23:51 -0700)
Add method (GET, POST, etc) to routing error message

f5749105e585128c0d84a2899e88ea684436d7a3 (2013-05-22 13:21:43 -0700)
Mount middlewares in matador's routes 

R=@dpup
R=@azulus