debug: Add support for more attributes for the debug info. * `debug_render_not_empty`: don't render an "empty" label if not attributes or items have been rendered for an object. * `debug_render_doc_dynamic`: render dynamic doc-string.

language: python
python:
  - "3.4"
install:
  - "pip install -r requirements.txt"
  - "pip install -r dev-requirements.txt"
script: py.test