Log Message:
Update blockdiag to 1.4.3.

History
=======

1.4.3 (2014-07-30)
------------------
* Show warnings on loading imagedrawers in debug mode
* ImageDraw#image() accepts Image objects
* Fix bugs

  - PNG: could not load png imagedrawer if could not access PIL.PILLOW_VERSION

1.4.2 (2014-07-12)
------------------
* SVG: Adjust text alignment precisely
* Add plugin events: node.changing and cleanup
* ImageDraw#image() accepts image from IO objects
* Fix bugs

  - PDF: Fix failure text rotating
  - PDF: Fix failure pasting PNG images (256 palette/transparency)
  - PNG: Fix background of node was transparent on pasting transparent images