chore(package): update eslint to version 6.6.0

Closes #22

Author: greenkeeper[bot]

package.json

@@ -18,7 +18,7 @@
   },
   "devDependencies": {
     "chai": "^4.0.2",
-    "eslint": "^5.0.0",
+    "eslint": "^6.6.0",
     "eslint-config-lesshint": "^1.0.3",
     "mocha": "^6.0.0",
     "proxyquire": "^2.0.0",