I design by @1x,why i use slicer It always generate @1x icon, i don't need @1x png,how should i do ? <img width="81" alt="2016-11-22 14 20 05" src="https://cloud.githubusercontent.com/assets/19890798/20513154/12c853a6-b0bf-11e6-939f-535c58d567d5.png">