Today I try to install specific laravel version with composer create-project laravel/laravel=5.1.8 your-project-name --prefer-dist, because some of the plugins have
composer create-project laravel/laravel=5.1.8 your-project-name --prefer-dist
A simple answer i can think of is
composer create-project laravel/laravel "5.1.*"
Just replace < app name > with your application name and you'll install laravel's 5.1 distribution.