Fix stale_lock?
Merge remote-tracking branch 'origin/master' into fix_stale_lock_method
Add tests for stale_lock?
Add test: impossible to enqueue duplicate job if worker still running

Test taken from https://github.com/tdtran/resque-uniq/pull/8
Merge pull request #13 from tdtran/fix_stale_lock_method

Fix: it's possible to enqueue duplicate jobs