Merge pull request #69 from walmartlabs-asdaios/master

Update SDTableViewSectionController to handle a crash in UITableView
Added a mechanism to perform a block when one or more operations have completed.
Changed project name of the new SDCompletionGroup class.
Renamed the dispatch queue.
acquire should return an id, not a instancetype.
Fixed an issue when using image composition for adornment menus and order of operations that would yield incorrect adornment image widths.
Updated pullnav sample app to use the adornment with image composition.
Merge remote-tracking branch 'upstream/master'