message: Set contributing guidelines as a markdown for doc.
diff: @@ -101,7 +101,7 @@ function(ginkgo_doc_gen name in pdf mainpage-in)
  ${doxygen_base_input}
  )
  # pick some markdown files we want as pages
  - set(doxygen_markdown_files "../../INSTALL.md ../../TESTING.md ../../BENCHMARKING.md")
  + set(doxygen_markdown_files "../../INSTALL.md ../../TESTING.md ../../BENCHMARKING.md ../../CONTRIBUTING.md")
  ginkgo_to_string(doxygen_base_input_str ${doxygen_base_input} )
  ginkgo_to_string(doxygen_dev_input_str ${doxygen_dev_input} )
  ginkgo_to_string(doxygen_image_path_str ${doxygen_image_path} )
  