fix(jenkins): Fix the format for passing parameters to Grunt tasks

The Jenkins build.sh script has to be updated as the previous way of
specifying parameters to the code run in Grunt tasks stopped working
with the newest Grunt. This has been previously fixed for the Travis
build.sh but wasn't done for the Jenkins one.

Also, the contribute docs were updated to account for the new format.

(cherry-picked from 5fc993361f355a0d656686c56a4e92082d140e6d)