ssh_keys not working on droplet create

I am trying to create a droplet, however, the ssh_keys array does not appear to get passed along during creation

``` ruby
[20] pry(main)> client.ssh_keys.find(id: 1234567)
=> 1234567, :@fingerprint=>"XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX", :@public_key=>"ssh-rsa XXXXXXXXXXXX", :@name=>"ssh key name"}>
[21] pry(main)> droplet
=> "new-droplet", :@size=>"2gb", :@image=>"centos-7-0-x64", :@region=>"nyc1", :@ssh_keys=>["1234567"], :@private_networking=>true, :@backups=>nil, :@ipv6=>nil, :@id=>nil, :@memory=>nil, :@vcpus=>nil, :@disk=>nil, :@locked=>nil, :@created_at=>nil, :@status=>nil, :@backup_ids=>nil, :@snapshot_ids=>nil, :@action_ids=>nil, :@features=>nil, :@networks=>nil, :@kernel=>nil, :@size_slug=>nil, :@user_data=>nil}>
[22] pry(main)> server = client.droplets.create(droplet)
=> "new-droplet", :@size=>nil, :@image=>14782842, :@name=>"7.1 x64", :@distribution=>"CentOS", :@slug=>"centos-7-0-x64", :@public=>true, :@regions=>["nyc1", "sfo1", "nyc2", "ams2", "sgp1", "lon1", "nyc3", "ams3", "fra1", "tor1"], :@type=>"snapshot"}>, :@region=>"nyc1", :@name=>"New York 1", :@sizes=>["512mb", "8gb", "16gb", "32gb", "48gb", "64gb", "1gb", "2gb", "4gb"], :@available=>true, :@features=>["private_networking", "backups", "ipv6", "metadata"]}>, :@ssh_keys=>nil, :@private_networking=>nil, :@backups=>nil, :@ipv6=>nil, :@id=>11162726, :@memory=>2048, :@vcpus=>2, :@disk=>40, :@locked=>true, :@created_at=>"2016-02-16T20:01:36Z", :@status=>"new", :@backup_ids=>[], :@snapshot_ids=>[], :@action_ids=>nil, :@features=>["virtio"], :@networks=>#, :@kernel=>6028, :@name=>"CentOS 7 x64 vmlinuz-3.10.0-229.20.1.el7.x86_64", :@version=>"3.10.0-229.20.1.el7.x86_64"}>, :@size_slug=>"2gb", :@user_data=>nil}>
[23] pry(main)> server.ssh_keys
=> nil
[24] pry(main)>
```