add __version__ info properly

[Ali Hürriyetoglu]

after an "import relevancer", relevancer.version should give the installed version of the library.

[Ali Hürriyetoglu]

http://stackoverflow.com/questions/17583443/what-is-the-correct-way-to-share-package-version-with-setup-py-and-the-package

http://stackoverflow.com/questions/458550/standard-way-to-embed-version-into-python-package

If we start a module, and an init.py in it, it may be practical to keep the version variable in that file. Check what is practical.