Add epub/pdf/mobi supporting

[zbutfly]

I found the great lib: spub.js.

So the work is in plan....

<script src="../dist/epub.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jszip/3.1.5/jszip.min.js"></script>
<div id="area"></div>
<script>
  var book = ePub("url/to/book/package.opf");
  var rendition = book.renderTo("area", {width: 600, height: 400});
  var displayed = rendition.display();
</script>