Drop only Selenium verbose logging rather than all output

This helps debugging mistakes leading to a java error (for instance
downloading the JAR from the wrong URL).

Author: stof

bin/run-selenium.sh

@@ -9,4 +9,4 @@ sleep 4
 echo '    Downloading selenium'
 curl -L http://selenium-release.storage.googleapis.com/2.49/selenium-server-standalone-2.49.1.jar > selenium.jar
 echo '    Running selenium'
-java -jar selenium.jar > /dev/null 2>&1 &
+java -jar selenium.jar -log /tmp/webdriver.log > /tmp/webdriver_output.txt 2>&1 &