Override title for chatlog links.

Makes the tooltip that appears when hovering over a link to show the target url, rather than the misleading date when underlying message was sent.

An example of current behavior:

![image](https://cloud.githubusercontent.com/assets/1924134/2869634/d58887de-d27e-11e3-80c5-12f18297fa91.png)

The vast majority of links on the internet have a title relevant to the destination, rather than the source. This PR fixes that.