Depend on the same docker version everywhere

The dependency in the Berksfile has been set to '>= 0.25.0', but the
metadata dependency hasn't which makes Chef pick the old version
(0.24.2). This causes deployments to fail due to the 'source' method
being unavailable
Depend on the latest nginx recipe

This fixes a dependency issue with build-essential. All other packages
depend on build-essential >= 0.0.0, whereas nginx-2.2.2 depends on
build-essential ~> 1.4.0
Merge pull request #20 from bauglir/master

Updated dependencies break deployment