Implement durable queues.

Queues are polled with an atomic 'lpoplpush' method to store a job on an
in-flight list. If a worker is terminated immediately while processing a,
that job is requeued. Otherwise it is just removed from the in-flight list.

An additional process can be used to requeue jobs in the case a worker was
terminated improperly (e.g. via a SIGKILL).
Add unit tests for durable queues.
Merge pull request #44 from danieldk/reliable-queues-left

Implement durable queues
Updated list of contributors.
Fix typo.
Allow tests to be independent. Failed when trying to release.
Use latest release plugin. 
See
http://stackoverflow.com/questions/15166781/mvn-releaseprepare-not-committing-changes-to-pom-xml.
[maven-release-plugin] prepare release jesque-2.0.0
[maven-release-plugin] prepare for next development iteration
Update README to reflect latest release.
Dependency version bumps
Merge branch 'master' of https://github.com/gresrun/jesque
Fixed logic error in addAll()
Fixes Issue #47
Added test for invokeSetters().
More tests on createObject().
Merge branch 'master' of https://github.com/gresrun/jesque
Reduction of Issue #46