rootFromDsl() now returns a Node object which wraps the raw vertex
add some methods to Node
verify() now can take a node
treeFromDsl() is now private in dsl.spec.js
stop using .targets() in evaluation.js, visualization.js
isSeq()
isFork(), isSeq()
extract TYPE_FORK
node.key -> node.key()
Node.payload -> Node.payload()
build the tree during translation
remove obsolete code
inline variable
.forEach -> .map
get rid of root.type
a node can carry a name
in a seq get rid of target vertices
in a fork, get rid of target vertices
node now holds its own key
Node now holds its own payload