Mention vars_files before the Roles section

The Roles section assumes some familiarity with vars_files, which this note attempts to briefly provide.
Links are the best kinds of instructions

Link people right to this page on Github, so they can click "edit" right there. No need for them to search for the repo, figure out that the docsite isn't a separate repo, and navigate to the given dir.
Nit fix spelling of separate
Merge pull request #2737 from jkleckner/more-spelling

Nit fix spelling of separate
Allow play tagging in context of new meta-tasks.
Merge pull request #2734 from chadoh/patch-2

Documentation: Links are the best kinds of instructions
Merge pull request #2731 from stoned/flush_handlers-cleanup

handlers must be run once
Empty plays should still gather facts
Fix test so that it is /bin/sh compliant (issue #2742)

The old test used syntax that appeared to be bash-specific and did not
work on platforms where /bin/sh did not point to bash.  See issue #2742
where copy to solaris hosts failed with the error:

    output: {'stdout': '', 'stderr': '/bin/sh: test: argument expected\n',
             'rc': 1}
Merge pull request #2745 from sfromm/issue2742

Fix test so that it is /bin/sh compliant (issue #2742)
Add region parameter and changed connection code.
Merge pull request #2746 from lwade/ec2region

Add region parameter and changed connection code.
Add region support to ec2 volume module.
Allow the environment string to be referenced by a bare variable name like:

environment: foo
Allow variables to be used raw in with_nested
Merge pull request #2747 from lwade/ec2_vol_region

Add region support to ec2 volume module.
Smush the braces in various places (hey, that rhymes) to avoid undo key=value splitting surprises
in new template system.
Allow args: var to be used to pass a variable in bare, and also templated versions should also DWIM.
Make --list-tasks work nicer with --tags
If sudoing and the sudo user is not root, the original file is saved as you, therefore delete that file as you.