Releasing coplan-engine

Publish the coplan-engine gem to RubyGems.org.

Steps

1. Bump the version

Edit engine/lib/coplan/version.rb and update CoPlan::VERSION to the new version number.

2. Commit the version bump

git add engine/lib/coplan/version.rb
git commit -m "Bump version to vX.Y.Z"

3. Tag the release