Grouped bar chart shows up as stacked bar chart after migration.

[yigitserin]

Hey there, I just recently migrated my app from Swift 2.3 to 4.1, and some api changes broke how my bar chart worked. Basically it shows up as a stacked bar chart instead of grouped bar chart and x axis labels are not gone.

Details and code is here:
https://stackoverflow.com/questions/49653956/how-to-create-a-grouped-bar-chart-in-swift

[liuxuan30]

well you have to look at chart demos and see #1474