Update build.

Author: kentwalters

dst/index.js

@@ -52,9 +52,11 @@ var Retool = /*#__PURE__*/function (_React$Component) {
     _this = _super.call(this, props);
 
     _defineProperty(_assertThisInitialized(_this), "startListening", function () {
-      window.addEventListener('message', function (e) {
-        return _this.handle(e);
-      });
+      if (_this.iframe) {
+        window.addEventListener('message', function (e) {
+          return _this.handle(e);
+        });
+      }
     });
 
     _defineProperty(_assertThisInitialized(_this), "startWatchers", function () {
@@ -131,6 +133,7 @@ var Retool = /*#__PURE__*/function (_React$Component) {
       }
     });
 
+    if (!_this.props.url) throw new Error('Please pass a url into the Retool component.');
     _this.state = {
       url: props.url,
       elementWatchers: {}

dst/package.json

@@ -1,6 +1,6 @@
 {
   "name": "react-retool",
-  "version": "0.2.0",
+  "version": "0.2.1",
   "private": false,
   "repository": {
     "type": "git",

package.json

@@ -38,7 +38,7 @@
     "build": "react-scripts build",
     "test": "react-scripts test",
     "eject": "react-scripts eject",
-    "publish:npm": "rm -rf dst && mkdir dst && babel src/components -d dst --copy-files && mv ./dst/Retool.js ./dst/index.js && cp ./package.json ./dst/package.json"
+    "publish:npm": "rm -rf dst && mkdir dst && babel src/components -d dst --copy-files && mv ./dst/Retool.js ./dst/index.js && cp ./package.json ./dst/package.json && cp ./README.md ./dst/README.md"
   },
   "eslintConfig": {
     "extends": [