Revert "add prepare to support install package from github"

This reverts commit 55e0c16.

Author: zimuliu

package.json

@@ -11,7 +11,6 @@
     "test": "npm run lint && npm run testonly",
     "testonly": "mocha --check-leaks --exit --full-trace --require ts-node/register 'src/**/__tests__/**/*-test.{ts,tsx}'",
     "dist": "npm run clean && tsc && npm run build",
-    "postinstall": "npm run clean && npm run dist",
     "prepublish": "npm run clean && npm run dist"
   },
   "directories": {