Add timeout around execution of external Python program

[benjastudio]

It would be useful to let the user define a timeout value when using the decorator @execute.python().

Eg:

import time
def sleep_and_return(seconds):
    time.sleep(seconds)
    return seconds

func = execute.python(timeout=0.5)(sleep_and_return)  # <== adding a new "timeout" parameter
result = func(10)  # <== It would be nice to raise after 0.5 seconds.