Bug 1413507 - Travis: Update to geckodriver 0.19.1 (#2895)

https://github.com/mozilla/geckodriver/releases/tag/v0.19.1
https://searchfox.org/mozilla-central/source/testing/geckodriver/CHANGES.md

.travis.yml

@@ -212,7 +212,7 @@ matrix:
         # to work around: https://github.com/travis-ci/travis-ci/issues/4873
         - if [[ ! -f ~/venv/bin/activate ]]; then virtualenv -p python ~/venv; fi
         - source ~/venv/bin/activate
-        - curl -sSfL https://github.com/mozilla/geckodriver/releases/download/v0.19.0/geckodriver-v0.19.0-linux64.tar.gz | tar -zxC $HOME/bin
+        - curl -sSfL https://github.com/mozilla/geckodriver/releases/download/v0.19.1/geckodriver-v0.19.1-linux64.tar.gz | tar -zxC $HOME/bin
         - nvm install 8.7.0
         # Use newer yarn than that pre-installed in the Travis image.
         - curl -sSfL https://yarnpkg.com/latest.tar.gz | tar -xz --strip-components=1 -C "$HOME"