Return the output of the render() method to the caller

Change-Id: I1e4f934f34bb6ddc9b1498ee70e6fc0ee88f458a
Multiple Enhancements

Added A3 paper size
Provided ability to set margins relative to opposite edge
Added code to save fill colour when rendering rectangles so that text
is still the same colour the next time it is written
Added text justification options to writeText()
Added drawLine() method

Change-Id: I6337a5b90692d57a08d99348155fb2be04ba8a4c
Merge branch 'master' of https://github.com/jamesggordon/Wrap_Pdf