fix(package): update less to version 3.6.0

Closes #388

Author: greenkeeper[bot]

package.json

@@ -67,7 +67,7 @@
     "flux": "3.1.2",
     "font-awesome": "4.7.0",
     "glicko2": "0.8.4",
-    "less": "2.7.2",
+    "less": "3.6.0",
     "lodash": "4.17.4",
     "mkdirp": "0.5.1",
     "npm-run-all": "4.0.2",