Upgrade to eslint 4, disable no-useless-escape rule

.eslintrc

@@ -55,6 +55,7 @@
         "no-unused-expressions": "error",
         "no-unexpected-multiline": "error",
         "no-unused-vars": "warn",
+        "no-useless-escape": "off",
         "no-void": "error",
         "no-warning-comments": "warn",
         "no-with": "error",

package.json

@@ -44,7 +44,7 @@
     "ecstatic": "~2.2.0",
     "editor-layer-index": "osmlab/editor-layer-index.git#gh-pages",
     "gaze": "~1.1.1",
-    "eslint": "~3.19.0",
+    "eslint": "~4.0.0",
     "glob": "~7.1.0",
     "happen": "~0.3.1",
     "js-yaml": "~3.8.1",