Fix static-file README.me in cl-dot.asd
Support pseudo-HTML in some label attributes

Now, in addition to the previously accepted objects, these label
attributes accept objects of the form

  (:html (ATTRIBUTES) (:ELEMENT (ATTRIBUTES) CHILDREN ...) ...)

Such a structure is translated into the HTML subset accepted by
GraphViz (including escaping of <, >, & and ", but without validation)
and <...> delimiters are added as required.
Support url, target and stylesheet attributes
Support ports in attributed and edge classes

Ports can be referenced via the :{source,target}-port initargs of the
attributed and edge classes. It is not checked whether the named ports
have actually been declared in any node labels.