Separate build script

Also configures this to run the build on npm publish or a deploy to
heroku.

Author: rylnd

package.json

@@ -7,10 +7,12 @@
   },
   "scripts": {
     "test": "mocha --exit",
+    "build": "babel src/ --out-dir=dist/ --copy-files",
     "dev": "concurrently --kill-others --prefix=name --names=server,eslint --prefix-colors=green,magenta \"babel-watch --watch src src/server.js\" \"esw src/ --changed --watch\"",
     "start": "babel-node src/server.js",
     "start:prod": "node dist/server.js",
-    "prepublishOnly": "babel src/ --out-dir=dist/ --copy-files"
+    "heroku-postbuild": "npm run build",
+    "prepublishOnly": "npm run build"
   },
   "author": "",
   "license": "MIT",