ui: Add a not-implemented popup

lib/ui/helpers.dart

@@ -0,0 +1,26 @@
+import 'package:flutter/material.dart';
+
+Future<void> showNotImplementedDialog(String feature, BuildContext context) async {
+  return showDialog<void>(
+    context: context,
+    barrierDismissible: false,
+    builder: (BuildContext context) {
+      return AlertDialog(
+        title: Text("Not Implemented"),
+        content: SingleChildScrollView(
+          child: ListBody(
+            children: [
+              Text("The $feature feature is not yet implemented.")
+            ]
+          )
+        ),
+        actions: [
+          TextButton(
+            child: Text("Okay"),
+            onPressed: () => Navigator.of(context).pop()
+          )
+        ]
+      );
+    }
+  );
+}

lib/ui/pages/conversations.dart

@@ -5,6 +5,7 @@ import 'package:moxxyv2/ui/pages/conversation.dart';
 import 'package:moxxyv2/models/conversation.dart';
 import 'package:moxxyv2/redux/state.dart';
 import 'package:moxxyv2/ui/constants.dart';
+import "package:moxxyv2/ui/helpers.dart";
 
 import 'package:flutter_speed_dial/flutter_speed_dial.dart';
 import 'package:flutter_redux/flutter_redux.dart';
@@ -75,7 +76,7 @@ class ConversationsPage extends StatelessWidget {
         children: [
           SpeedDialChild(
             child: Icon(Icons.group),
-            onTap: () => print("OK"),
+            onTap: () => showNotImplementedDialog("groupchat", buildContext),
             backgroundColor: BUBBLE_COLOR_SENT,
             // TODO: Theme dependent?
             foregroundColor: Colors.white,