Error when installing Lumen framework with Composer

When I run

sudo composer global require "laravel/lumen-installer=~1.0"

I get an error (below) that says it failed to download elfet/php-ssh.

Changed current directory to /Users/chad/.composer
./composer.json has been updated
Loading composer repositories with package information
Updating dependencies (including require-dev)
  - Installing elfet/php-ssh (v1.1.0)
    Downloading: Connecting...    Failed to download elfet/php-ssh from dist: The "https://api.github.com/repos/elfet/php-ssh/zipball/439becf180272542cbf154df4856a49dd3c4bf04" file could not be downloaded (HTTP/1.1 404 Not Found)
    Now trying to download from source
  - Installing elfet/php-ssh (v1.1.0)
    Cloning 439becf180272542cbf154df4856a49dd3c4bf04



  [RuntimeException]
  Failed to clone git@github.com:elfet/php-ssh.git via git, https, ssh protocols, aborting.
  - git://github.com/elfet/php-ssh.git
    Cloning into '/Users/chad/.composer/vendor/elfet/php-ssh'...
    fatal: remote error:
      Repository not found.
  - https://github.com/elfet/php-ssh.git
    Cloning into '/Users/chad/.composer/vendor/elfet/php-ssh'...
    remote: Repository not found.
    fatal: repository 'https://github.com/elfet/php-ssh.git/' not found
  - git@github.com:elfet/php-ssh.git
    Cloning into '/Users/chad/.composer/vendor/elfet/php-ssh'...
    Permission denied (publickey).
    fatal: Could not read from remote repository.

    Please make sure you have the correct access rights
    and the repository exists.