feat: allow node >=6 (testing-library#26)

Author: Whoaa512

package.json

@@ -17,7 +17,7 @@
   "author": "Kent C. Dodds <kent@doddsfamily.us> (http://kentcdodds.com/)",
   "license": "MIT",
   "engines": {
-    "node": "> 6"
+    "node": ">=6"
   },
   "scripts": {
     "add-contributor": "kcd-scripts contributors add",