Resolved #53

I added `primaryCapabilityProvider="false"` to the executable tag. Bamboo gets confused if you define multiple executables with the same type as primary capability. https://developer.atlassian.com/display/BAMBOODEV/Tasks+Overview#TasksOverview-Tasks,RequirementsAndCapabilities
Apart from that you can't manually select "ruby" as an executable on the server capabilities page. I don't know if that's intentional...