Fix spinner button spinning background

Fixes #107

routes/_components/IconButton.html

@@ -6,7 +6,7 @@
           :disabled
           delegate-key="{{delegateKey}}"
           focus-key="{{focusKey || ''}}" >
-    <svg class="icon-button-svg" ref:svg>
+    <svg class="icon-button-svg {{svgClassName || ''}}" ref:svg>
       <use xlink:href="{{href}}" />
     </svg>
   </button>
@@ -18,7 +18,7 @@
           focus-key="{{focusKey || ''}}"
           :disabled
           on:click >
-    <svg class="icon-button-svg" ref:svg>
+    <svg class="icon-button-svg {{svgClassName || ''}}" ref:svg>
       <use xlink:href="{{href}}" />
     </svg>
   </button>

routes/_components/compose/ComposeToolbar.html

@@ -6,7 +6,7 @@
       on:click="onEmojiClick()"
     />
     <IconButton
-      className="{{$uploadingMedia ? 'spin' : ''}}"
+      svgClassName="{{$uploadingMedia ? 'spin' : ''}}"
       label="Add media"
       href="{{$uploadingMedia ? '#fa-spinner' : '#fa-camera'}}"
       on:click="onMediaClick()"