Eric

Results 2 issues of Eric

I replaced the png files to webp, and get error `TypeError: unsupported file type` How to use it? @isair @priezz @dbasedow

@Jpadilla1 I want to use stacked bars, is this supported? ![32f93bdc-af20-11e5-8240-32dc80f951ac](https://cloud.githubusercontent.com/assets/182790/17576917/9ffae34e-5faa-11e6-8377-c459dd4b75f0.jpg)