Rafts and Pronterface

I'm trying to get rid of a nasty warp that keeps affecting all of my prints and I thought if I could print with a raft it would help the quality of my prints. I didn't use to have this problem when I was printing in ABS but now that I'm using PLA everything is contracting and warping a lot more even with a heated bed.

My first thought is to use a raft so that maybe the printed piece can float on a cushion of PLA and move when its contracting/cooling. My problem is I'm currently using pronterface/slic3r and it doesn't have an obvious raft option.

Is there a way to print with a raft in pronterface/slic3r or should I just move to a different program (maybe Repetier-Host)?