rhattersley's lazy-dtype branch

Since @rsignell-usgs is busy with the workshop here is a helping hand to generate the fixed iris packages for issue https://github.com/SciTools/iris/issues/1287

As soon as https://github.com/SciTools/iris/pull/1291 gets merged we should go back to the regular SciTools/iris master branch.
@rsignell-usgs The version string seem OK here.