fixed voice crop bug and bumped version to v0.3.1

frontend/index.html

@@ -30,7 +30,7 @@
         <button type="submit" class="btn btn-primary btn-block">Sign In</button>
       </form>
     </div>
-    <span class="version-label">v0.2.1</span>
+    <span class="version-label">v0.3.1</span>
   </div>
 
   <script src="/js/api.js"></script>