use functools.wrap for the TimeFuncton wrapper.

[rrraaaccc]

Applying the functools.wrap decorator is good practice and remains name and docstring of the original functions.

[rrraaaccc]

Maybe a short explanation of the problem is helpful.
With the current implementation of TimeFunction the Sphinx autoapi feature does not work properly, for all decorated functions. This is due to the renaming of the function by the decorator itself. The use of functools.wrap solve this well known problem and is best practice for python decorators.