Illustrate the HOA example with automata in SVG.
Fix missing BODY/END in last example automaton
Add `property: stutter-invariant`.  Closes #28.
Merge pull request #28 from adl/issue/28

stutter-invariant property
Mark `States:` as optionnal, but recommended.

Also remove a bogus `States: 1` from two 4-state examples.  This both
fixes an error in the document and demonstrate the possibility to omit
`States:`.

This closes #30.