Update carrierwave version

This version includes this fix:
https://github.com/carrierwaveuploader/carrierwave/pull/1517

There's no recent release so I've just pinned to the latest commit on master. Worryingly the carrierwave build is failing but the fix was only merged a few days ago...

@stevegraham @dan-palmer 
@stevegraham fixes this:
```
[Exception error="no implicit conversion of File into String" error_class=TypeError backtrace=/rails/app/presenters/jadu_xml/file_presenter.rb:11:
```
root cause is the carrierwave issue above. Agree should be ref, I was just guessing :-P

Might be hard to test because the issue is in the fog adapter. Oh and it seems to have borked a test too :-S