remediate acorn vulnerability

package-lock.json

@@ -30,9 +30,9 @@
             }
         },
         "acorn": {
-            "version": "3.3.0",
-            "resolved": "https://registry.npmjs.org/acorn/-/acorn-3.3.0.tgz",
-            "integrity": "sha1-ReN/s56No/JbruP/U2niu18iAXo=",
+            "version": "7.1.1",
+            "resolved": "https://registry.npmjs.org/acorn/-/acorn-7.1.1.tgz",
+            "integrity": "sha512-add7dgA5ppRPxCFJoAGfMDi7PIBXq1RtGo7BhbLaxwrXPOmw8gq48Y9ozT01hUKy9byMjlR20EJhu5zlkErEkg==",
             "dev": true
         },
         "acorn-globals": {
@@ -4530,6 +4530,14 @@
             "requires": {
                 "acorn": "^3.1.0",
                 "acorn-globals": "^3.0.0"
+            },
+            "dependencies": {
+                "acorn": {
+                    "version": "3.3.0",
+                    "resolved": "https://registry.npmjs.org/acorn/-/acorn-3.3.0.tgz",
+                    "integrity": "sha1-ReN/s56No/JbruP/U2niu18iAXo=",
+                    "dev": true
+                }
             }
         },
         "wordwrap": {