added helper function to dodge_coord_x.R
added helper function to dodge_coord_x.R

From: Zach Skidmore <zskidmor@genome.wustl.edu>

git-svn-id: 274f1dac86931020afba6208eb04fedad756fa4a@113378 bc3139a8-67e5-0310-9ffc-ced21a209358

griffithlab/GGgenome,zskidmor/GGgenome,jkunisak/GenVisR,griffithlab/GenVisR,zskidmor/GenVisR,zlskidmore/GenVisR