Add README.md as description to st2client package
Fix st2client deb package

The st2client deb package was created but did not install correctly on ubuntu resulting in error pkg_resources.DistributionNotFound error when executing /usr/bin/st2. This update to st2client Makefile uses stdeb with the bdist_deb option to create the deb package.
Merge pull request #804 from StackStorm/STORM-716/st2-version

Fix st2client packaging