highlight current file in toc sidebar
make active book highlight in workspace picker
make toc highlighting work when clicking on a book in the picker
fix bug where you can't hide the active file
refactor toc to not rerender every time you click on stuff
cleaning up sidebar highlight behavior
prefix internal variables in controllers/routing::goEdit() with '_'
move logic for 'btn-link' class on sidebar elements out of JS and into template
use single class for active elements of sidebars, differentiate with media type
refactor mixins/tree::hasChild() to hasDescendant() and make it more backboney
put conditional contextModel logic back into controllers/routing
used findDescendant to get the 1st element to open up in the content view
add depth first search to trees to find the first piece of content to open

also, set `_current*` to be the dereferenced Model because content may
appear in more than one book
change 'selected' attribute to '_selected' since it is a UI attribute

to match _isDirty and _hasRemoteChanges
Merge pull request #48 from oerpub/phil-selection-refactor

Phil selection refactor
Merge remote-tracking branch 'origin/master' into 57573740

Conflicts:
	scripts/views/workspace/sidebar/toc-branch.coffee
add back undefined test
fix typo causing book to not open on initial load
make the module editor look like a piece of paper (as in mock-up)
Merge pull request #47 from oerpub/57573740

book and file highlighting in sidebars