Added sdist option to setup to build a tarball

I tried to add an option to setup.py that allows to build a release tarball, i didn't touch the project structure, so i had to include file by file into project root directory. I didn't test it using windows also. Please review this proposal -since I'm not a real python developer- that could help in building tarballs from github master (or any other branches).
Same -or similar- changes could be done to other projects.