Update to latest geckodriver, version 0.22.0 (#135)

Author: stephendonner

.travis.yml

@@ -15,7 +15,7 @@ jobs:
       node_js: stable
       addons:
         firefox: latest-nightly
-      env: TOXENV=py36 MOZ_HEADLESS=1 GECKODRIVER=0.21.0
+      env: TOXENV=py36 MOZ_HEADLESS=1 GECKODRIVER=0.22.0
       before_install:
         - wget -O /tmp/geckodriver.tar.gz https://github.com/mozilla/geckodriver/releases/download/v$GECKODRIVER/geckodriver-v$GECKODRIVER-linux64.tar.gz
         - mkdir $HOME/geckodriver && tar xvf /tmp/geckodriver.tar.gz -C $HOME/geckodriver
@@ -33,7 +33,7 @@ jobs:
       node_js: stable
       addons:
         firefox: latest-nightly
-      env: TOXENV=py27 MOZ_HEADLESS=1 GECKODRIVER=0.21.0
+      env: TOXENV=py27 MOZ_HEADLESS=1 GECKODRIVER=0.22.0
       before_install:
         - wget -O /tmp/geckodriver.tar.gz https://github.com/mozilla/geckodriver/releases/download/v$GECKODRIVER/geckodriver-v$GECKODRIVER-linux64.tar.gz
         - mkdir $HOME/geckodriver && tar xvf /tmp/geckodriver.tar.gz -C $HOME/geckodriver