graphite source uri changed

Graphite project has been moved from Launchpad to Github. 
Version 0.9.10 is available at both locations, but 0.9.11 and newer (0.9.12, to the moment) can be found at Github only. This can be easily fixed by just overriding attribute node['graphite']..['uri'] in role, but changing a cookbook is better because it avoids unnecessary role complexity.
replace all node['apache']['user'] occurences with node['graphite']['user_account'].
make carbon-* Upstart scripts 0.9.12 compatible.
Not sure if it is Carbon source or underlying Twisted-11.1,
but ver. 0.9.12 carbon Upstart job should not expect daemon.
Merge pull request #100 from anatolijd/master

make it Graphite-0.9.12 ready.