TraversalSpec should return VertexNameSpec when property or method is missing

[moaxcp]

Problem

When traversals are used outside of the dsl it would be nice if they acted as expected when using a VertexNameSpec.

Test

The following test sets root to A. If the call to A created a VertexNameSpec.

given:
def names = []
graph.breadthFirstTraversal {
    root A
    visit { vertex ->
        names << vertex.name
    }
}

expect:
names == ['A', 'B', 'D', 'E', 'C']

Tasks

Add propertyMissing to TraversalSpec which returns a VertexNameSpec. Add appropriate tests to 'nondsl' test package.