Fix for digital object file versions

File versions with non parsable URI's cannot display in View mode.
Instead a server error (URI::InvalidURIError) is returned:

ActionView::Template::Error (bad URI(is not URI?)

Examples:

C:\Program Files\windows.exe
\\SomeAwesome\Network\location.bat
http://www.yr.no/sted/Finland/Västra_Finland/Askainen/varsel.xml

This patch acts defensively by catching the exception and displaying
the file_uri string if it does not parse as a URI.
Merge pull request #76 from mark-cooper/file_versions_fix

Fix for digital object file versions