fix(package): update less to version 3.5.1

Closes #17

Author: greenkeeper[bot]

package.json

@@ -43,7 +43,7 @@
     "imagemin-mozjpeg": "^7.0.0",
     "imagemin-pngquant": "^5.0.0",
     "inflection": "^1.12.0",
-    "less": "^2.7.1",
+    "less": "^3.5.1",
     "less-plugin-clean-css": "^1.5.1",
     "node-notifier": "^5.2.1",
     "node-sass": "^4.5.0",