Blockdiag

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* SVG: Adjust text alignment precisely
* Add plugin events: node.changing and cleanup
* ImageDrawimage() 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

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* Change interface of docutils node (for sphinxcontrib module)
* Fix bugs

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* Support embedding SVG/EPS images as background
* Use wand to paste background images that is not supported by Pillow (if installed)
* Add options to blockdiag directive (docutils extension)

- \:width:
- \:height:
- \:scale:
- \:align:
- \:name:
- \:class:
- \:figwidth:
- \:figclass:

* actor shape supports label rendering

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* Add diagram attribute: default_node_style
* Fix bugs

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* Fix bugs

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* Fix bugs