Update esprima to 4.0.1

Author: TimvdLippe

package.json

@@ -32,7 +32,7 @@
     "dependencies": {
         "estraverse": "^4.2.0",
         "esutils": "^2.0.2",
-        "esprima": "^3.1.3",
+        "esprima": "^4.0.1",
         "optionator": "^0.8.1"
     },
     "optionalDependencies": {