Support IPython 8

[devstein]

Closes #747

Description

IPython.core.interactiveshell.InteractiveShell.write and
IPython.core.interactiveshell.InteractiveShell.write_err have been deprecated since IPython 5 and were finally removed in IPython 8. This removes the deprecated method calls. I also bumped the minimum ipython version to 5. I don't see a reason to support 4.

cc @utkarshgupta137

Checklist

• Wrote a description of my changes above
• Added a bullet point for my changes to the top of the CHANGELOG.md file
• Added or modified unit tests to reflect my changes
• Manually tested with a notebook
• If adding a feature, there is an example notebook and/or documentation in the README.md file