triannon tests should clear test objects out of fedora

[ndushay]

@cbeer is there a simple way (fedora or LDP shortcut) to either

• delete all the child objects, recursively, of a fedora object, while keeping the parent object, via HTTP request or
• delete all the objects in a fedora repository via HTTP request

[ndushay]

Use after or other handy rspec construct

[ndushay]

• [x] integration tests
  • [x] choice
  • [x] content_as_text
  • [x] external uris
  • [x] no body
  • [x] specific resource
  • [x] Solr
• [x] annotation model
  • [x] solr docs
• [x] annotations controller
  • [x] create
  • [x] show
  • [x] index
  • [x] destroy
• [x] IIIF Anno list
• [x] LdpWriter
• [x] search controller
• [x] solr searcher
• [x] solr writer
• [x] viewing an anno

[ndushay]

This will be closed after a PR for #132 .