Time execution of function. Returns (res, seconds).

    >>> res, timing = timeit(time.sleep, 1)

def timeit(func, *args, **kwargs):
    """
    Time execution of function. Returns (res, seconds).

    >>> res, timing = timeit(time.sleep, 1)
    """
    start_time = time.time()
    res = func(*args, **kwargs)
    timing = time.time() - start_time
    return res, timing