Reverse dependencies for perpetuity

Latest version of the following gems require perpetuity

Gem	Version	Date	Downloads
perpetuity-postgres +26.5 Thousand Downloads	`0.0.9` August 14, 2016	August 14, 2016	26.5 Thousand
perpetuity-memory +9.78 Thousand Downloads	`0.2.0` January 13, 2014	January 13, 2014	9.78 Thousand
perpetuity-mongodb +5.1 Thousand Downloads	`1.0.0.beta2` September 25, 2014	September 25, 2014	5.1 Thousand