* Change behavior to behaviour
- use existing fact to get hash setting rather than shell task
- fix code highlighting syntax in playbooks_variables.rst
* Re-wrote intro section; this entire topic needs a clean-up/rewrite.
This change corrects problems reported by the `yamllint` linter.
Since key duplication problems were removed in 4d48711, this commit
mainly fixes trailing spaces and extra empty lines at beginning/end of
files.
