Major features not currently covered by tests:
- The quote-like operator
- Constructor:
  - Instantiaiton from a blessed object
  - Passing an argument hash to make a query string
- Methods:
  - set_auth
  - assert_content_type
  - has_response_assertions
  - findnodes
  - to_feed
  - uri
  - cancel
  - opengraph
- Request body serialization from:
  - hashref
    - to YAML
    - to JSON
    - to application/x-www-form-urlencoded
    - to multipart/form-data
  - arrayref
    - to YAML
    - to JSON
    - to application/x-www-form-urlencoded
    - to multipart/form-data
  - XML::LibXML::Node
    - to HTML
    - to XML
  - RDF::Trine::Model
    - to XML
    - to JSON
    - to Turtle
  - Check that unknown objects throw an exception
- Check auto-do_request in DESTROY works properly