Depend on your phalcon version, choose one of follow:
composer require phalcon-devtools:dev-master
composer require phalcon-devtools:v3.1.x-dev
composer require phalcon-devtools:v3.0.x-dev
composer require phalcon-devtools:v2.1.x-dev
composer require phalcon-devtools:1.x-dev
composer require phalcon-devtools:2.0.x-dev