Make @asynchronous's added 'handler' argument be keyword instead of positional

Adding a positional argument caused a problem when
@authenticated_api_view started using @has_request_variables
internally.  The 'handler' argument used to be passed through
positionally to the wrapped function, but when using
@has_request_variables, the wrapper inside @authenticated_api_view
had to take additional arguments.  The handler argument was then
assigned to one of those parameters instead of being passed through.

(imported from commit 66240bd465c803ddcbf4a603509051fca7381468)

zephyr/decorator.py

@@ -20,7 +20,7 @@ def asynchronous(method):
     @wraps(method)
     def wrapper(request, *args, **kwargs):
         try:
-            v = method(request, request._tornado_handler, *args, **kwargs)
+            v = method(request, handler=request._tornado_handler, *args, **kwargs)
             if v == None or type(v) == types.GeneratorType:
                 raise TornadoAsyncException
         except _DefGen_Return, e: