Ease removal of whitespace for Powershell Write-Output and VBScript Echo

[chris-rock]

This PR implements a new strip method to handle stdout

Powershell

# Write-Output comes with a newline
describe powershell("Write-Output 'hello'") do
  its('stdout') { should eq "hello\r\n" }
  # remove whitespace \r\n from stdout
  its('strip') { should eq "hello" }
  its('stderr') { should eq '' }
end

VBScript:

describe vbscript('WScript.Echo "hello"') do
  its('stdout') { should eq "hello\r\n" }
  # remove whitespace \r\n from stdout
  its('strip') { should eq "hello" }
end

[arlimus]

Thank you @chris-rock !