chore(package): update espree to version 6.1.2

Closes #582

Author: greenkeeper[bot]

Diff for: package.json

@@ -25,7 +25,7 @@
         "chai-spies": "1.0.0",
         "coveralls": "3.0.3",
         "eslint": "5.16.0",
-        "espree": "5.0.1",
+        "espree": "6.1.2",
         "gulp": "4.0.2",
         "gulp-eslint": "5.0.0",
         "gulp-istanbul": "1.1.3",