timer decorator

A decorator timer, which can be used to measure the performance of the function/method.
It uses two ways to measure performance:

1. time.process_time()
2. time.perf_counter()
   In short, .perf_coutnter() counts overall time elapsed, while the .process_time() does not include time, when CPU was not active. For instance, it does not counts time when function waited for some kind of pesponse (like HTTP ones).