Fix typo
Update mocha and underscore
Formatting
Render expander icon if necessary when nodes are added with loadBranch (refs #79)
Fix callback tests
Ignore multiple calls to collapse or expand

Calling expand() on an already expanded branch node will not trigger
callbacks or any other logic again.
Move some logic from render to initialize (node)
Test formatting
Render branch expanded when adding nodes dynamically with loadBranch (fixes #79)