hallelujah/valid_email — pull request #45 by georgedrummond (2014-11-22 17:00:25+00:00)
Title: Cache queries for each domain when Rails.cache is available

Doing lots of MX/DNS lookups is slow and for performace reasons its preferable to cache queries for each domain.

This allows caching when ```Rails.cache``` is available and a caching duration is set for ValidEmail.