Update topmost README file
Merge pull request #168 from sortega/task/readme

Update topmost README file
Add Graphviz directory in doc/ with an initial actor supervision graph
Merge pull request #170 from apoloval/doc/graphviz

Add Graphviz directory in doc/ with an initial actor supervision graph
Merge pull request #169 from apoloval/task/39

Simplify `MessageForwarding` entity
Preliminary work on exchange refactor