chore(package): update eslint to version 6.7.0

Closes #28

Author: greenkeeper[bot]

package.json

@@ -35,7 +35,7 @@
     "chai": "^4.0.2",
     "codecov": "^3.0.0",
     "docdash": "^0.4.0",
-    "eslint": "^5.0.0",
+    "eslint": "^6.7.0",
     "istanbul": "^0.4.5",
     "jsdoc": "^3.4.3",
     "mocha": "^5.0.0",