chore(build): overwrite tsd files on npm install

Author: harryterkelsen

package.json

@@ -23,7 +23,7 @@
   },
   "scripts": {
     "preinstall": "node tools/npm/check-node-modules --purge",
-    "postinstall": "node tools/npm/copy-npm-shrinkwrap && node tools/chromedriverpatch.js && webdriver-manager update && bower install && gulp pubget.dart && tsd reinstall --config modules/angular2/tsd.json && tsd reinstall --config tools/tsd.json",
+    "postinstall": "node tools/npm/copy-npm-shrinkwrap && node tools/chromedriverpatch.js && webdriver-manager update && bower install && gulp pubget.dart && tsd reinstall --overwrite --config modules/angular2/tsd.json && tsd reinstall --overwrite --config tools/tsd.json",
     "test": "gulp test.all.js && gulp test.all.dart"
   },
   "dependencies": {