Test button_for_remove_from_collection with rails3 and 4

In rails 4 the `multiple: true` option causes the name of the hidden
field to be `batch_document_ids[][]` rather than the desired
`batch_document_ids[]`
Merge pull request #10 from projecthydra/fix_single_item_hidden

Test button_for_remove_from_collection with rails3 and 4