How to install drush 8 properly? I'm trying to install drush 8 via composer:

composer global require drush/drush:dev-master (source)

but it gives me drush version 7.0.0 which is without D8 integration...
I'm using Linux Mint 17.
For Ubuntu

export PATH="$HOME/.composer/vendor/bin:$PATH"
source $HOME/.bashrc
composer global require drush/drush:8.x