Reverse dependencies for falls_back_on

Latest version of the following gems require falls_back_on

Gem	Version	Date	Downloads
earth +483 Thousand Downloads	`1.2.1` January 29, 2014	January 29, 2014	483 Thousand
emitter +212 Thousand Downloads	`1.1.1` September 11, 2012	September 11, 2012	212 Thousand
earth-ruby19 +6.47 Thousand Downloads	`0.2.3` September 28, 2010	September 28, 2010	6.47 Thousand
emitter-ruby19 +5.7 Thousand Downloads	`0.1.4` September 28, 2010	September 28, 2010	5.7 Thousand