Adding version command support to DCE-CLI

[drmmarsunited]

Proposed changes

As described in issue https://github.com/Optum/dce-cli/issues/40, the current CLI does not support a command for observing version. In this change, code is introduced to allow for a version command to be run, that is based off of the current git tag.

Documentation for the new command was generated by Cobra as well. Happy to discuss a testing strategy for this command, if necessary, but I have not yet introduced one.

Types of changes

• [ ] Bugfix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Refactor (changes to code, which do not change application behavior)

Checklist

• [x] I have filled out this PR template
• [x] I have read the CONTRIBUTING doc
• [ ] I have added automated tests that prove my fix is effective or that my feature works
• [x] I have added necessary documentation (README.md, inline comments, etc.)
• [x] I have updated the CHANGELOG.md under a ## next release, with a short summary of my changes

[joshmarsh]

Thanks @drmmarsunited , this is great! I'm going through your PR now.