Optimize user setting page for mobile browser (#1924)

* Remove overflow because it blocks scrolling on mobile safari.

* Add “-webkit-overflow-scrolling: touch;” to enable smooth scroll on mobile safari and other webkit browsers.

* Use radio buttons in user setting page.

Because select tags with long text are not fit in the width of mobile devices.

* Add flex property to fit labels to devise width.

* Change font size of select.

It causes auto zooming on mobile safari.

app/assets/stylesheets/forms.scss

@@ -42,7 +42,7 @@ code {
     }
   }
 
-  .input.file, .input.select {
+  .input.file, .input.select, .input.radio_buttons {
     padding: 15px 0;
     margin-bottom: 0;
 
@@ -59,6 +59,15 @@ code {
     margin-bottom: 25px;
   }
 
+  .input.radio_buttons .radio label {
+    margin-bottom: 5px;
+    font-family: inherit;
+    font-size: 14px;
+    color: white;
+    display: block;
+    width: auto;
+  }
+
   .input.boolean {
     margin-bottom: 5px;
 
@@ -72,7 +81,8 @@ code {
 
     label.checkbox {
       position: relative;
-	    padding-left: 25px;
+      padding-left: 25px;
+      flex: 1 1 auto;
     }
 
     input[type=checkbox] {
@@ -182,6 +192,10 @@ code {
       }
     }
   }
+
+  select {
+    font-size: 16px;
+  }
 }
 
 .flash-message {