Get the Magento Open Source software using Composer

composer create-project --repository-url=https://repo.magento.com/ magento/project-community-edition=<version> <installation directory name>

where <version> is 2.1.0, 2.1.1, and so on
For example, to install Magento Open Source 2.1.1 in the magento2 directory:

composer create-project --repository-url=https://repo.magento.com/ magento/project-community-edition=2.1.1 magento2