Log Message:
Update blockdiag to 1.4.1.

1.4.1 (2014-07-02)
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* Change interface of docutils node (for sphinxcontrib module)
* Fix bugs

1.4.0 (2014-06-23)
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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

1.3.3 (2014-04-26)
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* Add diagram attribute: default_node_style
* Fix bugs