chore(deps): brotli 1.1.0 breaks under python 2

temporarily fix by pinning to brotli 1.0.9.

google/brotli#1074

Author: rouilj

.travis.yml

@@ -138,7 +138,7 @@ install:
   - if [[ $TRAVIS_PYTHON_VERSION != "3.4"* ]]; then pip install mistune==0.8.4; fi
   - if [[ $TRAVIS_PYTHON_VERSION != "3.4"* && $TRAVIS_PYTHON_VERSION != "2."* ]]; then pip install Markdown; fi
   - pip install 'markdown2<=2.4.8'
-  - pip install brotli
+  - pip install brotli==1.0.9
   # zstd fails to build under python nightly aborting test.
   # allow testing to still happen if the optional package doesn't install.
   - pip install zstd || true