Speed up run by updating homebrew only once https://github.com/osxc/xc-common/issues/13
Small improvements to user_image role

Added a check for presence of user_image and explicated some paths
Merge pull request #19 from jeanregisser/master

Speed up run by updating homebrew only once
Merge pull request #20 from ninjabong/user_image

Small improvements to user_image role