Reverse dependencies for prawn-format

Latest version of the following gems require prawn-format

Gem	Version	Date	Downloads
davidtrogers-cucumber +6.03 Thousand Downloads	`0.6.2` February 17, 2010	February 17, 2010	6.03 Thousand
PaulOstazeski-prawn +4.89 Thousand Downloads	`0.4.99` August 11, 2014	August 11, 2014	4.89 Thousand
mrb-dreams +3.91 Thousand Downloads	`0.0.0` August 11, 2014	August 11, 2014	3.91 Thousand