please add epub 3.x support,epub 3.x no toc.ncx file

[ag2s20150909]

please add epub 3.x support,epub 3.x no toc.ncx file

[jiakuan]

@ag2s20150909 Good idea. Will check it

[gotson]

@jiakuan i've experimented with that, but found that working with org.w3c.dom is really painful. Would you consider using JSoup in the project for XHTML parsing ?

[gotson]

or there might be something to salvage from psiegman/epublib#143

[jiakuan]

@gotson Jsoup would definitely be a better option. I will have a look when I get a chance.
Pull requests are welcome and appreciated.

[asm0dey]

@jiakuan since I'm already here, maybe I can help with it? Just poke me in the right direction and I'll replace :)

[jiakuan]

Here are two tasks:

1. Replace org.w3c.dom with JSoup to make our lives easier moving forward.
   The first task is quite straightforward: just search and replace the usage with JSoup in a few classes and ensure the tests still work.

2. Add support for EPUB 3.x.
   You could refer to this PR, though it’s unclear how much we can leverage from it. This task seems more significant and may require arranging a new set of tests for EPUB 3.x functionalities.