[POC] New utility script to find and replace version number

[nwithan8]

Description

• A new utility script, called via make prep-release version="x.x.x" date="xxxx-xx-xx" that will find and update version numbers in:
  • setup.py
  • easypost/constants.py
  • CHANGELOG.md
• version required for script/make step, date optional (will use today's date if not provided)

Testing

• Confirmed working via multiple manual tests

Pull Request Type

Please select the option(s) that are relevant to this PR.

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [x] Improvement (fixing a typo, updating readme, renaming a variable name, etc)

[Justintime50]

Let's have you demo this in the coming days to us. My concern is that we'd potentially overwrite a package version

[Justintime50]

Do we still want to pursue this? My thinking is it's easier to update 2-3 file versions than it is to build out automation for this heh. With the rest of the releasing process automated now, the version bump diff is an acceptable manual step to take.