add support for chef_environment
add chef_environment test
update website chef-client provisioner page
reorder chef_environment alphabetically
Merge branch 'add-chef-environment' of github.com:cfortier2/packer into cfortier2-add-chef-environment

Conflicts:
	provisioner/chef-client/provisioner.go
Merge branch 'cfortier2-add-chef-environment'
Update CHANGELOG