* class_inheritable_accessor is deprecated in Rails 3.1
Rails returns uploaded files that have content_type but sometimes returns blank. This makes it so it doesn't try to use rails blank types.
When the attachment is a temporary file from an upload it will not have a file extension more than likely. This means that MIME cannot determine the file and we fall down to 'file' command more than we should have to. requires raykrueger/wand@4268216