Update playbooks_vault.rst

very minor grammatical fix for readability
Keep track of role dependencies across plays

Also fixes a bug in which tags specified on top-level roles were
not being passed down to dependent roles.

Fixes #4656
Update debian install documentation to include dependency resolution
Update debian install documentation to include dependency resolution
Merge pull request #6299 from jimi-c/issue_4656_role_deps_across_plays

Keep track of role dependencies across plays
Merge pull request #6297 from ardentperf/patch-1

Update playbooks_vault.rst
Merge pull request #6300 from l0neranger/devel

Update debian install documentation to include dependency resolution
Micro-optimization of inventory.expand_hosts.detect_range
Micro-optimization: replace s.find(x)!=-1 with x in s

timeit shows a speedup of ~3x on Python 2.7.5 x86_64.
It also makes the code a bit shorter.
hostname module: don't filter hostnamectl with awk

There's no need to filter hostnamectl's output with awk because its man
page says:

    hostnamectl [OPTIONS...] {COMMAND}

       --static, --transient, --pretty
	   If status is used (or no explicit command is given) and one
	   of those fields is given, hostnamectl will print out just
           this selected hostname.

E.g. hostnamectl --static status => ansible.example.org