Removed the single assignment block from constraints
Generate /var/cache/<component> by default

This directory is used for keystone's signing-dir in most
services, so it makes sense to always create it
Merge pull request #44 from dirkmueller/release/stoney/master

Generate /var/cache/<component> by default
Merge pull request #42 from vuntz/release/stoney/master

Removed the single assignment block from constraints