Quick install Composer library manager on Ubuntu 16.04 to handle Drupal 8 libraries.
First, get Composer:
$cd ~ $sudo apt-get install curl $sudo curl -s https://getcomposer.org/installer | php
make Composer available globally:
$sudo mv composer.phar /usr/local/bin/composer
and you are done! You should get a similar output as in the next screenshot: