Added expires at column to response set
Added utility methods to survey and unit tests
Updated parse code to schedule affected response sets as expired
Updated survey to only update previous response sets
Created migration to set expiry on existing response sets
Added utility methods for checking if a certificate has expired
Added warnings when a certificate is expired or will expire soon
Ignored all ds store files
Modified migrations to add field to certificate instead
Moved certificate expiry logic to certificate class method
Updated helper methods
Updated tests
Bumped schema timestamp to try to make Jenkins update the database
Merge pull request #648 from theodi/certificate-expiry-reporting

Certificate expiry reporting