Address issue in which multipe node reference were created for a tooltip. Address issues with orphaned text in ie6, 7, 8. Fix #1285. Fix #1293"
	modified:   js/ChartBase.js
Addressed issue with leftover text nodes in chart's legend. Addressed edge cases with leftover tooltip contents in chart.
    modified:   js/CartesianChart.js
	modified:   js/ChartBase.js
	modified:   js/ChartLegend.js
Clean up chart's series-tests unit test for ie.
	modified:   tests/unit/assets/series-tests.js
Remove unused variable from CartesianChartLegend.
	modified:   js/CartesianChartLegend.js
Add destructor method to PieChart. Fix #1139.
	modified:   js/PieChart.js