[feature] Add automatic version detection

[sdepold]

Add support for auto-detecting which version fragment to bump:

npm_release --auto --auto-fallback minor

This will parse the git history and check every commit since the tag that corresponds with the current project version and HEAD. The commit's subject and body will be scanned for certain markers:

• [major] will generate a major version bump
• [minor], [feature] will generate a minor version bump
• [patch], [bugfix], [fix] will generate a patch version bump

[seangates]

Is the default going to be --auto or something else?

[sdepold]

Until further testing I would not make it the default and once we feel it works well we can make a major bump and rna or it by default