Bump to 1.6.1 and use version from submodule

Use the version from the submodule for the gem version. So it is
consistent with other types of toolkit packages.

Change the jenins.sh to update the version of the submodule as part of jenkins.sh and commit the updated submodule after the gem has been published. I can then update jenkins to push the master branch as a post build step.
I am not sold about moving it into gem_publisher myself. Changing the contents of the gem and pushing that back to a remote feels like a pre-publish step to me and not a publish concern. I can see the merit in reusing the `version_released?` logic rather than relying on string comparison, however getting at that from bash isn't possible and it seems odd to move the git bash commands into the ruby Rakefile.