Add a version / upgrade check

[bmuenzenmeyer]

Add logic similar to yarn, but for pattern lab

warning Your current version of Yarn is out of date. The latest version is "1.0.2" while you're on "0.27.5".
info To upgrade, run the following command:
$ npm upgrade --global yarn

[riktimmondal]

Is it still open?

[bmuenzenmeyer]

no this is complete. i forgot to label this.