Changed deletes and downloads for checked resources.

This addresses bug #451 and adds feature #458.  Specifically, when deleting or downloading large numbers of items, the process would fail because the query string for the GET and DELETE methods would exceed allowed sizes.  The downloads have been switched to using a form submit process.  The deletes use a body on the rest request.  Since bodies on deletes are only partially allowed (they aren't supported via phantom and jasmine, as far as I can tell), I also added the ability to send a POST request with an X-HTTP-Method-Override header (or its variants) that allows using a POST and redirecting to a DELETE.  The testing was updated to reflect this.
Improved the coverage of checkbox downloads.
Update coverage thresholds to avoid coverage regressions
Update coverage thresholds to avoid covg regression
Merge pull request #482 from girder/update-covg-thresholds

Update coverage thresholds to avoid coverage regressions
Upgrade to jquery v2.1.1, and use the more official npm package
Merge pull request #481 from girder/large-numbers-of-checked-items

Fixed delete and download on large numbers of checked items.
Merge pull request #483 from girder/jquery-v2

Upgrade to jquery v2.1.1, and use the more official npm package
Merge remote-tracking branch 'origin/master' into jobs
Add the notion of scopes to the token model