rename script resource to powershell resource

[chris-rock]

script = <<-EOH
# you powershell script
EOH

# old syntax is using `script` resource
describe script(script) do
  its('stdout') { should eq 'output' }
end

# new syntax is using `powershell` resource
describe powershell(script) do
  its('stdout') { should eq 'output' }
end

[arlimus]

Much clearer and less confusing, fantastic improvement!
Let's get script deprecated for 1.0 🎉