Removing support for node < 6, since the 4.x LTS is only good for a few more months, and most people are on newer versions already. Also adding testing for node 9
Removing support for node < 6, since the 4.x LTS is only good for a few more months, and most people are on newer versions already. Also adding testing for node 9

natecavanaugh/check-source-formatting,natecavanaugh/check-source-formatting,natecavanaugh/check-source-formatting