fix: tag name should not be bumped if bump is disabled in options

Currently, I bump the version of the app with another Grunt task, then generate the changelog with https://github.com/btford/grunt-conventional-changelog, then I run this task to commit, tag, push, and publish.

Unfortunately, `bump: false` in the options just prevents this task from saving the bumped version, but it still uses the updated version to tag and commit.

This patch fixes the issue so that if `bump` is set to `false`, grunt uses the old version number for the commit and tag.