Paragraph spacing for userzoom test

Temporary user preference for a userzoom study.

Control it like this,

* http://localhost:9000/world/2013/jul/19/g20-report-warns-global-tax-chaos#gu.prefs.paragraphSpacing=none
* http://localhost:9000/world/2013/jul/19/g20-report-warns-global-tax-chaos#gu.prefs.paragraphSpacing=indents
* http://localhost:9000/world/2013/jul/19/g20-report-warns-global-tax-chaos#gu.prefs.paragraphSpacing=more