update root version?

[fengpinghu]

We have a user who is interested in using this notebook image to scale out his analysis with Dask.
The root version built in the image is 6.28.12, but he needs 6.32. Is it possible update the root version to 6.32?

[matthewfeickert]

We'll try to do so in PR #67, but there's currently some build issues for our test project. c.f. #67 (comment)