Require ruamel namespace package

[jakirkham]

Rebuilds the package with the ruamel namespace package to avoid clobbering between different packages using the namespace.

cc @jjhelmus @mariusvniekerk

Checklist

• [x] Used a fork of the feedstock to propose changes
• [x] Bumped the build number (if the version is unchanged)
• [ ] Reset the build number to 0 (if the version changed)
• [x] Re-rendered with the latest conda-smithy (Use the phrase code>@<space/conda-forge-admin, please rerender in a comment in this PR for automated rerendering)
• [x] Ensured the license file is being packaged.

[conda-forge-linter]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe) and found it was in an excellent condition.

[jakirkham]

Have gone ahead and merged to move things forward. Please let me know if there are any issues.