Install wget on ubuntu 16.04
Install wget on ubuntu 16.04

We get an unbounded variable error when attempting to use `perl` to
perform the file download. As other Ubuntu docker images have `wget`,
let's install it for consistency. The hab-install.sh script should be
updated upstream so that the `perl` based installation works, though.

Signed-off-by: Joshua Timberman <d6955d9721560531274cb8f50ff595a9bd39d66f@chef.io>

chef-cookbooks/habitat,chef-cookbooks/habitat,chef-cookbooks/habitat