Backport LoadError fix into 1.0.x

This has been done in 'master' and the newer versions of redis-store but not in the 1.0.x branch, which is what's used by default on Rails 2.3.8 and Ruby 1.8.7 (I know, I know....I'm working on the upgrade!)

Anyway, this should fix people's complete inability to use redis-store 1.0.x.