Merge pull request #818 from mjonas87/master

Improved infinite loop avoidance in autoSizeColumns()
Implement lazy totals calculation in the DataView.

Add a ‘lazyTotalsCalculation’ grouping info option (default = false)
that delays the totals calculation until the item is accessed via
getItem(index).  This can dramatically improve the perceived
performance of the DataView operations on very large datasets.
Optimize DataView group collapse/expand.
Fix a typo
Merge branch 'upstream-master'