improve Resource object:  - add make_params and make_headers methods allowing you to modify    headers and params - add unauthorized method allowing you to react on 401/403, return True   by default - make sure default pool is only set one time in the main thread - fix __call__ and clone methods.
improve Resource object:
 - add make_params and make_headers methods allowing you to modify
   headers and params
- add unauthorized method allowing you to react on 401/403, return True
  by default
- make sure default pool is only set one time in the main thread
- fix __call__ and clone methods.

benoitc/restkit,openprocurement/restkit