dougal/acts_as_indexed — pull request #43 by parndt (2013-01-22 03:16:57+00:00)
Title: Ensure that thread is required when using Mutex on Ruby 1.8.7

This used to be loaded by, I believe, Rake but not anymore.

My tests were failing only on Ruby 1.8.7:
https://travis-ci.org/refinery/refinerycms-acts-as-indexed/jobs/4297230/#L139