Merge pull request #69 from Connexions/multiple-mediatypes

Add support for one model handling multiple media types
Merge pull request #68 from Connexions/paths-in-ids

Support content with '/' in the id
Sidebar DnD is enabled on the wrong element

It must be an element with the data-media-type attribute for dropzones
to work properly
Merge branch 'hotfix-dragging' into github-refactor
Getting children of a Tree Node uses getChildren

instead of assuming a Backbone attribute named 'contents'
Merge branch 'toc-getchildren' into github-refactor
Use the mediaType in the container XML file

instead of hardcoding to OPF mediaType
Support basic navigation tree rendering

Does not remove duplicates or allow inserting after the current node.