Rough wiring for bulk actions - still has some issues

* Select all stops working after a couple of tries
* No confirmation on publish/unpublish/delete
* Publish/Unpublish can fail weirdly if there are required fields.
Fix posts select all function - use .prop() not .attr()

For more info see:
http://ejohn.org/blog/jquery-16-and-attr/
http://stackoverflow.com/questions/5874652/prop-vs-attr
Add notification for success/failure when bulk unpublishing/published posts
Add confirmation dialog, and notifications when bulk deleting posts
Clean up formatting of chained calls in PostItemView
Maintain 'selected' state on the item view
Fix bulk publish button - set status to correct value
Delegate selected/unselected checks in post list to itemView, rather than dom

Check selected values on the itemViews, rather than the checkboxes in DOM.
Set selected values using select() unselect() calls
Load models from view, not collection.
Merge pull request #210 from ushahidi/post-bulk-actions

Wire up posts bulk action toolbar