PR geerlingguy#16: Style change, use false instead of no for bool.

Fixes geerlingguy#19: Sign into MAS fails with Ansible 2.8.

Also test on 10.14 Mojave.

Fixes geerlingguy#12: Drop 10.11 from test builds since mas doesn't s…

…upport it anymore.

Merge pull request geerlingguy#6 from MikeSouza/master

Add MAS CLI signin dialog (--dialog) support

Merge pull request geerlingguy#3 from jeromegamez/feature/check-accou…

…nt-status

Don't sign in if already signed in

Fix templating issue in when conditional, and add examples.