Convert timeout to a float instead of a string

The "request_timeout" argument gets converted to a string here in the utils._escape function :  https://github.com/elasticsearch/elasticsearch-py/blob/c112399631a9bfb8517f1483051c5ba5510951e6/elasticsearch/client/utils.py#L62

Later, "request_timeout" gets popped and passed into def perform_request() as the "timeout" argument, still as a string, leading to a type error. -- The "timeout" kwarg expects a float.

casting to a float() seems to fix it.