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.
take REDIS_URL from settings if exists
Merge remote branch 'original/master'
deprecate use of host/db/port options for Redis
Use a redis set to store queue names, instead of relying on the redis "keys" method,
which does not perform well on large databases.
Fix: COMPACT_QUEUE should be a unique key.

This fixes #230.  Thanks, @sylvinus.
Update changelog.
PEP8ify.
PEP8ify.
Merge branch 'pricingassistant-master'
PEP8ify.
Merge branch 'asldevi-master'
Store birth and death values as UTC dates.
Merge branch 'master' into job_dependency

Conflicts:
	rq/job.py
	rq/queue.py