m src/main/scala/com/signalcollect/AbstractVertex.scala
m src/main/scala/com/signalcollect/examples/Sssp.scala

Minor: Changed AbstractVertex.scoreCollect default implementation

Used to return the size of the iterable, now returns 1 for sizes >= 1
and 0 for size 0.
The function gets called often, but the actual size is irrelevant for
all current implementations. This makes it reasonable to change the
default to something more efficient.