Fix some installation related issues

This PR fix some installation related issues

* Fixes these warnings during installation:

        warning: no files found matching 'README.txt'
        warning: install_data: setup script did not provide a directory for 'examples\Vera.ttf' -- installing right in '...'

* Set classifiers to indicate this project supoorts both Python 2 and 3

* Add long_description in setup, the description will appear on PyPI after next register

Thanks for this great library.