Update for oh-my-zsh playbook

[zuernBernhard]

Hi, i could not run the playbook wiith current ansible binary on Kubuntu 15.10. 64 bit because of a deprecation warning for using "sudo" instead of "become" and the variable access did not work until $user was changed to {{user}}. See my Pull-Request for the solution: https://github.com/RaymiiOrg/ansible/pull/3