Set prpl-server to proxy bots to http://rendertron

This will proxy bots to http://rendertron but if the address does not
exist it quickly falls back to serving directly. This will be used for
internal DNS usage in our production servers

Author: WillMoggridge

package.json

@@ -24,7 +24,7 @@
     "polymer-build": "npm-run-all 'polymer build {@}' --",
     "polymer-lint": "npm-run-all 'polymer lint {@}' --",
     "polymer-serve": "npm-run-all 'polymer serve {@}' --",
-    "prpl-server": "prpl-server --root build/ --host 0.0.0.0 --port 80",
+    "prpl-server": "prpl-server --root build/ --host 0.0.0.0 --port ${PORT:-80} $(if [ -n \"${BOT_PROXY:-}\" ]; then echo \"--bot-proxy ${BOT_PROXY}\"; fi)",
     "serve": "npm-run-all 'serve-examples {@}' --",
     "serve-examples": "./bin/serve $(if [ -z \"$*\" ]; then echo \"examples\"; fi)",
     "serve-live": "./bin/serve",