Add :use_cursor option to PrawnOutputter, which makes it use and update Prawn's built-in cursor

This lets you output a human-readable barcode like this:

barcode = Barby::QrCode.new("http://toretore.eu/barby/")
Prawn::Document.generate("test.pdf") do |pdf|
  pdf.text "Visit this website:"
  barcode.annotate_pdf(pdf, :use_cursor => true)
  pdf.text barcode.data
end
Add horizontal and vertical alignment support to PrawnOutputter

This lets you output a human-readable barcode with centered text like this:

barcode = Barby::QrCode.new("http://toretore.eu/barby/")
Prawn::Document.generate("test.pdf") do |pdf|
  barcode.annotate_pdf pdf, :align => :center, :use_cursor => true
  pdf.text barcode.data, :align => :center
end
Add :text option to PrawnOutputter, allowing easy human-readable barcodes to be generated

Example:

  Prawn::Document.generate("test.pdf") do |pdf|
    Barby::EAN13.new("987654321098").annotate_pdf pdf, :text => true
  end
Merge fork with prawn outputter improvements git://github.com/dlitz/barby into prawnimprove