chore(package): update eslint to version 6.4.0

Closes #15

Author: greenkeeper[bot]

package.json

@@ -19,7 +19,7 @@
     "babel-plugin-transform-es2015-modules-commonjs": "^6.26.0",
     "codecov": "^3.0.0",
     "cz-conventional-changelog": "^2.1.0",
-    "eslint": "^4.19.1",
+    "eslint": "^6.4.0",
     "eslint-config-prettier": "^2.9.0",
     "eslint-plugin-import": "^2.10.0",
     "eslint-plugin-jest": "^21.15.0",