Pretty-print request params on exception page

Bringing some love to query params formatting on exception page.

Before:
![screen shot 2014-12-01 at 01 02 17](https://cloud.githubusercontent.com/assets/522155/5241917/4bf39cd8-78f6-11e4-97b5-630c901ca142.jpg)

After:
![screen shot 2014-12-01 at 01 02 00](https://cloud.githubusercontent.com/assets/522155/5241918/505ab856-78f6-11e4-9ede-d162ee851880.jpg)