Examples fail on Windows

[krzysztofarendt]

When running examples using multiprocessing on Windows, the following errors pops out:

RuntimeError:                                                                                                                                                                                                                                                           An attempt has been made to start a new process before the                                                                                                                                                                                                      current process has finished its bootstrapping phase.                                                                                                                                                                                                                                                                                                                                                                                                                                                                           This probably means that you are not using fork to start your                                                                                                                                                                                                   child processes and you have forgotten to use the proper idiom                                                                                                                                                                                                  in the main module:                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 if __name__ == '__main__':                                                                                                                                                                                                                                          freeze_support()                                                                                                                                                                                                                                                ...                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     The "freeze_support()" line can be omitted if the program                                                                                                                                                                                                       is not going to be frozen to produce an executable.          

It is because Windows requires the code using multiprocessing to be enclosed with the condition:
if __name__ == '__main__'.

The examples work fine on Linux.

There should warning about this also in README.