FIX: expand t.co links to show original link

Example:

![screen shot 2014-08-29 at 19 43 48](https://cloud.githubusercontent.com/assets/5732281/4092914/f48f564c-2f96-11e4-9c43-daa4384158a8.png)

Notice `t.co` link expands to `meta.discourse.org/t/how-to-updat…`