CSS to show link on hover

Great plugin. Can I propose a simple CSS change to make the button appear only on hover in thumbnail view. This avoid obscuring the lower part of the thumbnail.

Replace line 2 of the CSS file with these two lines.

.copy-media-url .thumbnail-wp-cmu-copy-btn{position: absolute;bottom:0;z-index: 999;width: 100%;opacity: 0;}
.copy-media-url .thumbnail-wp-cmu-copy-btn:hover {opacity: 1;}