Added script for the generation of state diagrams

[AlkisPlas]

This provides a first approach to the declarative specification and drawing of UML state diagrams.

[dspinellis]

Interesting. Please add examples and documentation (under doc).

[dspinellis]

• Regarding the interface please make it as follows

stategraph [-o output_file] [-v] [input file]

If no files are given, it acts as a filter from stdin to stdout
-v is used for view

• Use getopt to parse the arguments
• The customary dot extension is .dot, but you shouldn't be using it in the code as an implicit extension. Use whatever the user provides.

[AlkisPlas]

I have already changed the interface that way but I did it using the argparse module.
Would you like me to use getopt instead?
The result will be the same.

[dspinellis]

argparse is fine.