A few small tweaks to the README.

Fixes geerlingguy#42: Add configure_dotfiles variable so you can disa…

…ble dotfiles management.

Fixes geerlingguy#15, geerlingguy#42: Don't take over everyone's git …

…commit karma by default.

Merge pull request geerlingguy#41 from geerlingguy/40-deprecated-casks

Fixes geerlingguy#40: Remove deprecated homebrew casks.

Merge pull request geerlingguy#38 from generoi/issue-34

Issue geerlingguy#34: Change osx setup script to be configurable

Fixes geerlingguy#11: Use mas for Mac App Store automation.

Issue geerlingguy#25 Follow-up: Fix path to config.yml.

Fixes geerlingguy#25: Make it easier to override configuration/vars.

Make play run on only 127.0.0.1, not 'localhost' also.

Updated instructions for ansible-playbook command.