Refs #77 - Using 'engine' in query string instead of 'x-diecutter-template-engine' header to guess the engine to use. Deprecated 'template_engine' and 'filename_template_engine' headers in favor of 'engine' and 'filename_engine'.
Refs #77 - Restored doctests in Sphinx documentation. Using '.directory-tree' instead of '.diecutter-tree', as expected by piecutter.