Minor cleanup (#220)

* Fix README; add missing dev dependency

* Fix validators to filter out bad events and sources

* Better defaults in config

src/components/Toolbar.js

@@ -184,6 +184,7 @@ class Toolbar extends React.Component {
     return (
       <div
         className={classes}
+        key={iconKey}
         onClick={() => {
           this.selectTab(_selected);
         }}