Update minimum dependency versions.

Fixes #4

Author: goto-bus-stop

package.json

@@ -7,18 +7,18 @@
     "url": "https://github.com/browserify/acorn-node/issues"
   },
   "dependencies": {
-    "acorn": "^6.0.1",
+    "acorn": "^6.0.2",
     "acorn-dynamic-import": "^4.0.0",
-    "acorn-walk": "^6.0.1",
+    "acorn-walk": "^6.1.0",
     "xtend": "^4.0.1"
   },
   "devDependencies": {
-    "acorn-bigint": "^0.3.0",
+    "acorn-bigint": "^0.3.1",
     "acorn-import-meta": "^0.3.0",
-    "buble": "^0.19.3",
+    "buble": "^0.19.6",
     "mkdirp": "^0.5.1",
     "standard": "^11.0.1",
-    "tape": "^4.8.0"
+    "tape": "^4.9.1"
   },
   "homepage": "https://github.com/browserify/acorn-node",
   "keywords": [