refactor auth redirect and add ConditionalRedirect unit tests and App unit and functional tests

src/components/ConditionalRedirect.jsx

@@ -0,0 +1,22 @@
+import React from 'react';
+import {
+  Route,
+  Redirect
+} from 'react-router-dom';
+
+const ConditionalRedirect = ({ component: Component, shouldRedirect, redirectPath, ...props }) => {
+  if (shouldRedirect()) {
+    return (
+      <Redirect to={{
+        pathname: redirectPath,
+        state: { from: props.location }
+      }}/>
+    );
+  } else {
+    return (
+      <Route {...props} render={props => (<Component {...props}/>)} />
+    );
+  }
+};
+
+export default ConditionalRedirect;