second parameter of groupByNode() is 0 indexed
correct positioning for multiple highlighted stacked and staircase points, fix to #901
Merge pull request #902 from toni-moreno/fix_multiple_highlight_points

Fix #901: correct positioning for multiple highlighted stacked and staircase points
Merge pull request #895 from ngmlabs/master

second parameter of groupByNode() should be 0 indexed
legend html markup cleanup
Graph: Tooltip refactoring for testability
Merge remote-tracking branch 'upstream/master'