Add new version wkhtmltox binary and update referencies

* update wkhtmltopdf binary to 0.12.0 version on before_script.sh
* update docs to reference a wkhtmltopdf on github ( https://github.com/wkhtmltopdf/wkhtmltopdf )
* add link to official site http://wkhtmltopdf.org/
* move tests from MakeFile to run_tests.sh