Removed [from, to] from treemap defaults. Because $.extend doesn't overw...

"Removed [from, to] from treemap defaults. Because $.extend doesn't overwrite all the defaults when there are less than 2 drilldowns in the options. So in case of less than 2 drilldowns 'to' was added to the end of the array, even in cases where the dataset doesn't have 'to' as a drilldown. Thus causing errors. This solves that.