Only set backend if one is not already set

Version bump to 2.1.0.pre

Fixing problem with no Time.zone

Merge branch 'master' of [email protected]:keithmgould/delayed_job

Regenerated gemspec for version 2.0.3

Regenerated gemspec for version 2.0.2

Regenerated gemspec for version 2.0.1

Regenerated gemspec for version 2.0.0

Regenerated gemspec for version 1.8.6

Apparently Jeweler doesn't like pre-release gems

This reverts commit cff0fd2.