Fixing blockquotes

This hacks on the unmarshaler to add an Order field, so that the
paragraphs and quotes can be normalized and sorted.

Still need to hack on the marshaler so that paragraphs and quotes can be
passed together as an interface array.

Initial commit

Parses an EPUB archive into HTML. Currently dumps everything to STDOUT,
but can push into array and then sort according to table of contents.

Blockquotes are not handled correctly. Need to hack on (un)marshaler for
that to work correctly.

Titles are not always handled correctly. Need to look for more than just
h3 tags (i.e. h1, h2) and need to let these bubble up from div tags.