Epub support in Atril

This is how the project has come along. This week I'll be focusing mostly on fixing bugs, other than the night-mode(inverted colors) that I'm working on right now, If I have time later in the week, I will implement either Mathjax, or if that's not working, the Atril thumbnailer for epub, 

This currently has reading with thumbnails, searching, document properties, document index(table of contents), full screen mode etc. all with both GTK2(using webkit-1.0) and GTK3(written using the webkit2gtk API). Webkit has only been used in libview, and the ePub backend does not use any libraries other than what were already in use by Atril, other than the two minizip files which I added into a folder there itself.

Please look through this and give me any feedback you have, we can keep this open while I add the finishing,