CSS3 pulse animation for new message notifications fixing #398

Added pulse effect to buddies in buddy list when that buddy is sending a message, using CSS3 keyframe animations, because setInterval is the past and we live in the future now.

![hoverboard](https://f.cloud.github.com/assets/72914/981806/5ac8d00a-078e-11e3-8dad-67548d46c36d.gif)