Pass object into renderExpando function

Pass underlying object to renderExpando implementation so that expando may be customized on a row by row basis.
Add .dgrid-cell-editing class when editor is active.
editor: consistent quotes, remove redundant comments, add class sooner
Update CHANGES.md to reflect editor's dgrid-cell-editing class
tree: bail out of expand if already in desired state
Document tree expand bail-out in CHANGES.md
Change Grid#cell duck-type test to avoid errors w/ non-objects
editor: avoid errors if edit is called with unresolvable argument
Fix regression in test index page by using shouldExpand
Prevent error in test index page when no cookie has been set yet
tree: fix regression with re-expansion upon refresh
Test index page should not include itself in the list (indexception?!)
Update 0.3.6-dev references to 0.3.6 for tag
Update CHANGES.md and package.json version for dev towards 0.3.7
Fix #306, #406: Absolutely-position ColumnHider node and use icon
Update CHANGES.md to reference ColumnHider trigger fixes
Merge pull request #427 from pags/master

Pass object into tree.js renderExpando function.
tree: document renderExpando change in CHANGES.md
Fix #409: don't clobber classes when expanding/collapsing tree row
Document tree expando class preservation fix in CHANGES.md