First stab at writing implementing job dependency.
Don't enqueue waitlisted jobs on failed execution.
Avoid race conditions when enqueueing job with dependency.
Simplify enqueue_waitlist by using lpop.
Internally renamed the term "parent" to "dependency".
Merge branch 'master' of git://github.com/nvie/rq into job_dependency

Conflicts:
	rq/queue.py
Don't fail if job dependency is modified during enqueue process.
Use a redis set to store queue names, instead of relying on the redis "keys" method,
which does not perform well on large databases.
Store birth and death values as UTC dates.
Merge branch 'master' into job_dependency

Conflicts:
	rq/job.py
	rq/queue.py
Python 3 fixes for job dependency stuff.
Merge pull request #207 from selwin/job_dependency

Job dependency
Add job dependencies to the changelog.
Only save queue to set on enqueue.
Validate queue key still exists when all() is called
Merge remote-tracking branch 'upstream/master'

Conflicts:
	tests/test_queue.py
Remove misleading test.
Record new behaviour of Queue.all() explicitly in a test.
PEP8ify.
Update changelog.
Merge pull request #252 from nvie/use-utc

Store birth and death values as UTC dates