Extract Method: _getChangeTypes.
Order the version autocomplete based off of PR types. Fixes #11.

This tries to apply the rules of semver to the categorized pull requests
to guess what the appropriate version is for this release.

A backwards compatibility breaker indicates a major version bump.  Major
features indicates a minor version bump.  All other changes indicate a
patch version bump.
Merge pull request #18 from nubs/correct-versioning

Order the version autocomplete based off of PR types. Fixes #11.