Add clean script

script/clean.py

@@ -0,0 +1,20 @@
+#!/usr/bin/env python
+
+import os
+import sys
+
+from lib.util import rm_rf
+
+
+SOURCE_ROOT = os.path.abspath(os.path.dirname(os.path.dirname(__file__)))
+
+
+def main():
+  os.chdir(SOURCE_ROOT)
+  rm_rf('node_modules')
+  rm_rf('out')
+  rm_rf('spec/node_modules')
+
+
+if __name__ == '__main__':
+  sys.exit(main())