feat(build): initial SauceLabs setup

Closes #2347

scripts/sauce/sauce_connect_block.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+
+# Wait for Connect to be ready before exiting
+printf "Connecting to Sauce."
+while [ ! -f $BROWSER_PROVIDER_READY_FILE ]; do
+  printf "."
+  #dart2js takes longer than the travis 10 min timeout to complete
+  sleep .5
+done
+echo "Connected"