Turn off jasmine-node temporarily

The grunt-contrib-jasmine-node package has disappeared from npm, apparently replaced by grunt-jasmine-node. Unfortunately, when I just replaced grunt-contrib-jasmine-node with the new package, grunt could not find the jasmine-node task.So, this pull request just turns off jasmine-node for the time being so that Travis can pass. I'll take another look at grunt-jasmine-node when I get a chance (or if someone beats me to it, that'd be great too :smile:)