update: add postinstall to package.json

Author: unsigned6

package.json

@@ -17,6 +17,7 @@
     "test:unit": "mocha --compilers js:babel-core/register --colors --require should --reporter dot test/**/*.js",
     "test:cover": "babel-node ./node_modules/.bin/isparta cover --include './*.js' _mocha -- --require should",
     "prepublish": "npm prune && run-s build test",
+    "postinstall": "npm run compile",
     "watch": "npm run compile -- --watch"
   },
   "repository": {