Add missing onDragleave callback and add canUpload callback
Add canUpload and uploadDenied options
Add tests for upload permissions
Make sure grid is bound to ajax callbacks
Add addData method
Add jquery initialization
Add getRefreshHints method
getDataFrom server gets passed a `done` callback
Fix Tree::collapseAt and add HGrid::collapseAll
Working lazy-loading

plus updated examples
Fix getting item in expandItem
_loaded is set by _lazyLoad method

Update README
Merge branch 'lazy-loading' into develop
Build
onSuccess receives server response data

Also, fix the upload example
Build
Make uploadUrl and uploadMethods deferred

Allows async calls within these callbacks. For example, S3 needs to
make an ajax call to get a token for a bucket
Add Tree::destroy()
Add HGrid::emptyFolder
Simpler column schema