Add support for the notion of an embargo.  On core record pages and on the drs item partial asset download links are now conditional on the item not being embargoed.
Add check to block direct dl of an item that may be embargoed via the /downloads/ route
Update compilation download to ensure that embargoed items are filtered out of the zip compilation job.  Also update method in embargoable.rb to be under_embargo? to match with SolrDocument version.  Also, eliminate useless method from NuCollection.
Fix bug with implementation of fedora under_embargo?
Eliminate kruft from compilations show view.
Fix compilation actions bar to actually delete sets.
Update the zip compilation job so that before doing any other processing, it adds a very small hidden file to the zipfile.  This should allow the file to be created and downloaded even if a user assembles a set exclusively consisting of embargoed items that he has no current read access on.
Update embargo spec
Merge pull request #457 from NEU-Libraries/embargo_behavior

Embargo behavior