1. Department of Mathematical Sciences, Computer Science Division, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
2. Department of Physics and Electronics, Rhodes University, PO Box 94, Grahamstown 6140, South Africa
3. SKA SA, 3rd Floor, The Park, Park Road, Pinelands 7405, South Africa
4. INAF-Istituto di Radioastronomia, via Gobetti 101, I-40129 Bologna, Italy
5. Department of Astronomy, University of California, Berkeley, CA 94720, USA
6. Radio Astronomy Laboratory, University of California, Berkeley, CA 94720, USA