version to 2.18.0
version to 2.18.0

I'm doing a major version bump mostly b/c Asset now only supports
Ruby 2.4+.

* (hotfix) update dependencies 7c3205f
* (hotfix) update to cli.rb v1.1.0 b346037
* (hotfix) update to our latest style conventions afab624
* (hotfix) remove CircleCI for now 9dcfdd2

redding/assert