Install etcd from a tarball.

Fixes #1.

This change adds another recipe, `tar_install`, which installs etcd from a tarball. I've tested it against the v0.1.0 release from github.

    node[:etcd][:url] = 'https://github.com/coreos/etcd/releases/download/v0.1.0/etcd-v0.1.0-Linux.tar.gz'