Issue 16

How to test:

• Check out this branch.
• Create a batch set by running the islandora_compound_batch_preprocess drush command. You do not need to run drush islandora_batch_ingest. Using the mysql cli, confirm that the islandora_compound_batch table contains rows for the preprocessed objects.
• Repeat the instructions above to create a second batch set.
• Run drush islandora_compound_batch_prune_relationships. It should report that it has deleted 0 rows from the table.
• Visit http://localhost:8000/admin/reports/islandora_batch_sets and delete one of the batch sets.
• Run drush islandora_compound_batch_prune_relationships. It should report that it has deleted the number of rows from the table that were in the set you deleted.
• Using the mysql cli, confirm that the islandora_compound_batch table does not contain rows for the deleted objects.
• Also, make sure the new section I added to explain how to use this command makes sense. It has the heading 'Pruning the list of relationships'.