devkit: export amberc, configBuilder, helpers from index.js

external/amber-dev/index.js

@@ -0,0 +1,5 @@
+module.exports = {
+    "amberc": require('./lib/amberc'),
+    "helpers": require('./lib/helpers'),
+    "configBuilder": require('./lib/config')
+};

external/amber-dev/package.json

@@ -5,6 +5,7 @@
   "scripts": {
     "test": "echo \"Error: no test specified\" && exit 1"
   },
+  "main": "index.js",
   "repository": {
     "type": "git",
     "url": "git://github.com/amber-smalltalk/amber.git"