Reverse dependencies for falls_back_on

Latest version of the following gems require falls_back_on

Gem	Version	Date	Downloads
earth +497 Thousand Downloads	`1.2.1` January 29, 2014	January 29, 2014	497 Thousand
emitter +217 Thousand Downloads	`1.1.1` September 11, 2012	September 11, 2012	217 Thousand
earth-ruby19 +6.56 Thousand Downloads	`0.2.3` September 28, 2010	September 28, 2010	6.56 Thousand
emitter-ruby19 +5.78 Thousand Downloads	`0.1.4` September 28, 2010	September 28, 2010	5.78 Thousand