Merge remote-tracking branch 'upstream/master'
Address error in destroy method for pie chart.
Update charts unit tests.
Add `grunt import-pure` task to Pure Base and Grids modules into YUI

The Pure modules are imported into YUI's src/ tree until we ditch the
build/, then it will become a build thing only.
Import Pure Base and Grids
Upgrade `grunt-css-selectors` plugin which visits media queries

This fixes an issues where Pure Grids selectors inside media queries
were not being visited or replaced with `yui3-` selectors.
`stopPropagation` to avoid possibility of multiple file dialogs.
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
Valid `value` to ensure it is strictly numeric.
Addition of unit tests to ensure `Slider` only accepts numeric values.
Correction of `on` to `after`.
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
Removal of `validator` logic in setter.
Addition of validation logic in `_setNewValue`.
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
Changes from yui build. (no min changes)
	modified:   selector-native/selector-native-coverage.js
	modified:   selector-native/selector-native-debug.js
	modified:   selector-native/selector-native.js
	modified:   yui-base/yui-base-coverage.js
	modified:   yui-base/yui-base-debug.js
	modified:   yui-base/yui-base.js
	modified:   yui-core/yui-core-coverage.js
	modified:   yui-core/yui-core-debug.js
	modified:   yui-core/yui-core.js
	modified:   yui-nodejs/yui-nodejs-coverage.js
	modified:   yui-nodejs/yui-nodejs-debug.js
	modified:   yui-nodejs/yui-nodejs.js
	modified:   yui/yui-coverage.js
	modified:   yui/yui-debug.js
	modified:   yui/yui.js
Added Y.ArrayAssert.isUnique()
Build