Update all dependencies to latest versions.

Also verified that the list of modules is the same as
https://www.npmjs.com/package/node-libs-browser, and none of the packages
used to provide the stubs have changed (just their versions).

package.json

@@ -10,28 +10,28 @@
   },
   "dependencies": {
     "assert": "^1.4.1",
-    "browserify-zlib": "^0.1.4",
-    "buffer": "^4.9.1",
+    "browserify-zlib": "^0.2.0",
+    "buffer": "^5.2.1",
     "console-browserify": "^1.1.0",
     "constants-browserify": "^1.0.0",
-    "crypto-browserify": "^3.11.0",
-    "domain-browser": "^1.1.7",
-    "events": "^1.1.1",
-    "https-browserify": "0.0.1",
-    "os-browserify": "^0.2.1",
-    "path-browserify": "0.0.0",
-    "process": "^0.11.9",
-    "punycode": "^1.4.1",
+    "crypto-browserify": "^3.12.0",
+    "domain-browser": "^1.2.0",
+    "events": "^3.0.0",
+    "https-browserify": "^1.0.0",
+    "os-browserify": "^0.3.0",
+    "path-browserify": "^1.0.0",
+    "process": "^0.11.10",
+    "punycode": "^2.1.1",
     "querystring-es3": "^0.2.1",
-    "readable-stream": "^2.3.6",
-    "stream-browserify": "^2.0.1",
-    "stream-http": "^2.8.0",
-    "string_decoder": "^1.1.0",
-    "timers-browserify": "^1.4.2",
-    "tty-browserify": "0.0.0",
+    "readable-stream": "^3.3.0",
+    "stream-browserify": "^2.0.2",
+    "stream-http": "^3.0.0",
+    "string_decoder": "^1.2.0",
+    "timers-browserify": "^2.0.10",
+    "tty-browserify": "0.0.1",
     "url": "^0.11.0",
-    "util": "^0.10.3",
-    "vm-browserify": "0.0.4"
+    "util": "^0.11.1",
+    "vm-browserify": "^1.1.0"
   },
   "bundledDependencies": [
     "assert",