Updated README.md, python2 and 3 support, atomic and docker optional
Updated README.md, python2 and 3 support, atomic and docker optional

pthierry38/openscap-daemon,baude/openscap-daemon,OpenSCAP/openscap-daemon,pthierry38/openscap-daemon,baude/openscap-daemon,OpenSCAP/openscap-daemon