This started out as a general purpose proxy for POST and GET requests. hive-js needs it for getting around blockr's CORS issue specific to POST requests sent from safari. It has evolved to strip away unused data specifically for the /tx/raw/ endpoint to save on payload sent to client.
git clone git@github.com:hivewallet/hive-proxy.git
cd hive-proxy
npm install
CORS_ORIGINS=* npm start
open http://localhost:9009