Problem during install of drush..

[patoshii]

http://prntscr.com/c3ms72

./composer.json has been created
Loading composer repositories with package information
Updating dependencies (including require-dev)
Your requirements could not be resolved to an installable set of packages.

Problem 1
- Installation request for drush/drush dev-master -> satisfiable by drush/drush[dev-master].
- drush/drush dev-master requires codegyre/robo ~1.0.0-beta1 -> satisfiable by codegyre/robo[1.0.0-beta1] but these conflict with your requirements or minimum-stability.

Installation failed, deleting ./composer.json.

[titobrasolin]

In my opinion #13 solves the issue.
Thanks @jcmartinez !