Revert "Use 'prepare' instead of 'prepublish' in package.json"

See <https://github.com/Rush/publish-to-git/issues/4>

This reverts commit 927fbe3d65.

package.json

@@ -12,8 +12,9 @@
   },
   "main": "lib",
   "scripts": {
-    "prepare": "babel -d lib src",
+    "build": "babel -d lib src",
     "postpublish": "publish-to-git --force --tag latest",
+    "prepublish": "npm run build",
     "test": "ava"
   },
   "author": "Gerben <gerben@treora.com>",