Added support for Resque gem version 1.23.0

The current version of the gem requires version 1.22.0 of the Resque gem, however the current stable version of Resque is 1.23.0.  This updates the dependency to "~> 1.22", allowing version 1.23.0.  I updated the tests to ensure it works with both v1.22 and v1.23.