Prepare: Prepare 0.18.0 release

[CSSFrancis]

• Update the version number in release_info.py.
• Update the CHANGELOG.rst file with the date and new version number and a description of the changes.
• Update the list of contributors in both the release_info.py and .zenodo.json files.Make sure that the Zenodo file is valid JSON.
• Commit the changes and push them to the repository.
• Create a new tag with the “v” + version number (e.g. “v0.16.0”) and make a new release on GitHub.
• Wait for the CI server to finish the release process.

[CSSFrancis]

@pc494 this should be good to go. I drafted a release as well and will make the release first thing tomorrow assuming you don't have any major objections.