Generated cli is not compatible with windows.

`apitools/base/py/base_cli.py` uses [readline](https://pypi.python.org/pypi/gnureadline) which is not supported on Windows. Perhaps there is a way to use [pyreadline](https://pypi.python.org/pypi/pyreadline).

As a side note, it would be nice to separate cli code into separate package, because of some wildcard imports if generated cli is present it is being pulled in even if it is not used.