Update EPub.OPF.php

changed title-page to titlepage due to an error issued by idpf validator
Update EPub.php

add another elseif at the end addChapter for creating the TOC reference in TOC and NCX as if a subchapter. this allows implementators to put the toc anywhere they want.
TODO: delete link to toc in toc or delete toc line in toc
Update EPub.Example3.php

add line for TOC. can be place anywhere among the addChapter(s).
Merge pull request #13 from raqy/master

The changes look ok.