Option http method v2

Fixed PEP8 errors. And added the OPTION method for every URL. I don't know if I did it in the right way. I'm not really familiarized with Flask. @kennethreitz could you check if the `before_request` makes sense please? https://github.com/santiagobasulto/httpbin/commit/5c71fd5773f4f63d4c7fe2d0f0e050d6ad593b65

![captura de pantalla de 2014-06-03 10 40 08](https://cloud.githubusercontent.com/assets/872296/3164774/3c4a3e68-eb4d-11e3-9806-c4bb54a6232a.png)
![captura de pantalla de 2014-06-03 10 40 22](https://cloud.githubusercontent.com/assets/872296/3164773/3c49cc44-eb4d-11e3-8679-4091dc702632.png)