[Async] Enable async/await and update UIExplorer and tests

Summary:
- Enables async/await in .babelrc and transformer.js
- Adds regenerator to package.json. Users still need to explicitly require the regenerator runtime -- this is so that you only pay for what you use.
- Update AsyncStorage examples in UIExplorer to use async/await
- Update promise tests in UIExplorer to use async/await in addition to the promise API

Closes https://github.com/facebook/react-native/pull/1765
Github Author: James Ide <ide@jameside.com>

package.json

@@ -49,13 +49,13 @@
     "absolute-path": "0.0.0",
     "babel": "5.4.3",
     "babel-core": "5.6.4",
-    "chalk": "^1.0.0",
+    "chalk": "1.0.0",
     "connect": "2.8.3",
-    "debug": "~2.1.0",
-    "graceful-fs": "^3.0.6",
+    "debug": "2.1.0",
+    "graceful-fs": "3.0.6",
     "image-size": "0.3.5",
     "immutable": "^3.7.4",
-    "joi": "~5.1.0",
+    "joi": "5.1.0",
     "jstransform": "11.0.1",
     "module-deps": "3.5.6",
     "optimist": "0.6.1",
@@ -63,11 +63,12 @@
     "react-timer-mixin": "^0.13.1",
     "react-tools": "git://github.com/facebook/react#b4e74e38e43ac53af8acd62c78c9213be0194245",
     "rebound": "^0.0.12",
+    "regenerator": "0.8.31",
     "sane": "^1.1.2",
     "semver": "^4.3.6",
     "source-map": "0.1.31",
     "stacktrace-parser": "frantic/stacktrace-parser#493c5e5638",
-    "uglify-js": "~2.4.16",
+    "uglify-js": "2.4.16",
     "underscore": "1.7.0",
     "wordwrap": "^1.0.0",
     "worker-farm": "^1.3.1",