corrected python syntax, line 143 perfvis.py
corrected python syntax, line 143 perfvis.py

serendipiddy/Network-Visualization-and-Performance-Prediction,serendipiddy/openflow-performance-visualizer,serendipiddy/Network-Visualization-and-Performance-Prediction,serendipiddy/openflow-performance-visualizer,serendipiddy/openflow-performance-visualizer,serendipiddy/Network-Visualization-and-Performance-Prediction,serendipiddy/Network-Visualization-and-Performance-Prediction,serendipiddy/openflow-performance-visualizer,serendipiddy/Network-Visualization-and-Performance-Prediction,serendipiddy/openflow-performance-visualizer