Make search highlight more visible

The default one is very hard to notice. I guess i'm not the only one who thinks so.
![Screenshot](https://photos-1.dropbox.com/t/0/AAB5iyge-U5F1d0IWcdl9EeOQcQ1iK8PQeJMdRoTVo0nPw/12/14553166/png/2048x1536/3/1396612800/0/2/Screen%20Shot%202014-04-04%20at%2014.13.40.png/saa8f3ORYzfQQKcOBqe-Lm8BgFVroNIn3Jsa5yplCk4)