fix(fab): Remove transition for fabs on ng-hide.

Buttons currently have CSS to ensure they do not attempt any
transitions when they have the `ng-hide` class attached. The
`.md-fab` buttons were not receiving the same styles due to
a specificity issue.

Add the same styles for FABs that standard buttons have.

Fixes #5235.

Author: topherfangio

src/components/button/button.scss

@@ -141,6 +141,9 @@ button.md-button::-moz-focus-inner {
       height: $button-fab-mini-height;
     }
 
+    &.ng-hide, &.ng-leave {
+      transition: none;
+    }
   }
 
   &:not([disabled]) {