Markdown 3.3.6 available does is fix the failure with 3.3.5?

New release of Markdown is available. See if it works with roundup.

Author: rouilj

.travis.yml

@@ -104,7 +104,7 @@ install:
   - pip install pytest-cov codecov
   - if [[ $TRAVIS_PYTHON_VERSION != "3.4"* ]]; then pip install docutils; fi
   - if [[ $TRAVIS_PYTHON_VERSION != "3.4"* ]]; then pip install mistune; fi
-  - if [[ $TRAVIS_PYTHON_VERSION != "3.4"* && $TRAVIS_PYTHON_VERSION != "2."* ]]; then pip install Markdown==3.3.4; fi
+  - if [[ $TRAVIS_PYTHON_VERSION != "3.4"* && $TRAVIS_PYTHON_VERSION != "2."* ]]; then pip install Markdown; fi
   - pip install markdown2
   - pip install brotli zstd