Add the setuptools package configuration

Currently we can only use the debian package or the RPM package to
install python-midonetclient. It's not a trivial process to create these
packages and that makes adding new features harder. And it's not easy to
try this package out on Mac OSX.

This patch addds the setuptools package configuration, which makes us to
install python-midonetclient easier. We can also use virtualenv/venv to
separate the installation environments out from each other.

Because python-midonetclient is a public project, we can register this module
on PyPI. Feel free to register with the following command:

    $ python setup.py register

Signed-off-by: Taku Fukushima <tfukushima@midokura.com>
Add readline to the dependencies for Mac OSX

Some platforms i.e., Mac OSX don't support readline module in the
standard library. This patch adds the explicit dependency declaration to
setup.py to install readline module on the installation.

Signed-off-by: Taku Fukushima <tfukushima@midokura.com>