add nix-prefetch-zip
fix bzr prefetcher on darwin
require gnused for all prefetch scripts
Add gox and packer packages
update serfdom to v0.6.2
add etcd package
add etcdctl package
add fleet package
add nsq package
add gocode package
add camlistore package
Print output of `git describe` in `nix-prefetch-git`

I hope it will help make git-packages' versions much nicer

It's usually only useful in --deepClone is also specified.
Merge pull request #3037 from cstrahan/extra-fetchers

add nix-prefetch-zip
Merge pull request #3073 from tailhook/git-describe-in-prefetch

Print output of `git describe` in `nix-prefetch-git`
Merge pull request #3060 from cstrahan/packer

Add gox and packer packages
Merge pull request #3061 from cstrahan/serf-update

update serfdom to v0.6.2
Merge pull request #3062 from cstrahan/etcd

add etcd package
Merge pull request #3063 from cstrahan/etcdctl

add etcdctl package
Merge pull request #3064 from cstrahan/fleet

add fleet package
Merge pull request #3065 from cstrahan/nsq

add nsq package