Fix incorrect use of copy on list
Add note about su support
Merge pull request #6256 from angstwad/changes_changes-yo-dawg-i-herd-you-like-changes-so-commited-some-changes-into-changes-so-you-can-diff-while-you-diff

Add note about su support in CHANGELOG
minor typo in playbooks_variables.rst

so so, this should probably be fixed!
Update playbooks_variables.rst

Another minor typo.
Avoid range selection on empty groups

This prevents a traceback when the group is empty.
Fixes #6258
Merge pull request #6259 from arianitu/patch-1

minor typo in playbooks_variables.rst
Update CONTRIBUTING.md

docsite no longer has a subdirectory latest.
Merge pull request #6261 from arianitu/patch-2

Update CONTRIBUTING.md
Merge pull request #6260 from j2sol/6258

Avoid range selection on empty groups
Merge pull request #6248 from hkariti/fix_list_copy

Fix incorrect use of copy() on list, causing a traceback
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