chore(package): update mocha to version 6.2.1

Closes #118

Author: greenkeeper[bot]

package.json

@@ -41,7 +41,7 @@
     "is-ci": "^1.0.7",
     "istanbul": "^0.4.2",
     "jshint": "^2.8.0",
-    "mocha": "^5.0.2",
+    "mocha": "^6.2.1",
     "mocha-lcov-reporter": "^1.2.0",
     "mockery": "^2.0.0",
     "rimraf": "^3.0.0"