ws-3314: update example runner usage info

Author: Adam Soos

examples/run_examples.sh

@@ -1,5 +1,10 @@
 #!/bin/bash
 
+if [ $# -eq 0 ]; then
+    echo "Usage: $0 API_KEY [ALT_URL]" 1>&2
+    exit 1
+fi
+
 OPTS=""
 if [ -n "$2" ]; then
     OPTS="--url=$2"