Issue #70 - Display placeholder if Pig Visualizer has no data. Fix Auto Pan Zoom and Reset Pan Zoom buttons.
Issue #70 - Minor tweaks and add a message to refer user to full stats on JobTracker.
Issue #70 - Display counters in more details pane for Pig Visualizer.
Issue #70 - Fix grammar in comment.
Merge pull request #71 from davidzchen/pigvisualizer-robust

Pig Visualizer improvements