Pillowfight should have an option to do deletion

What's the issue?

Currently pillowfight does not have an option to simulate deletion of documents. This would be useful to have as then we could simulate workloads including document deletion.

What's the fix?

Add an additional option to pillowfight to delete documents. This could come in the form of setting pillowfight to populate a certain number of documents and also delete so in turn it would delete some documents as it runs and create new ones in their place.