Potential error of message construction of SCC

Hi,

According to the [paper](http://ilpubs.stanford.edu:8090/1077/3/p535-salihoglu.pdf), I think the message passing condition written in line 78 should be 

```scala
e.srcAttr._1 < e.dstAttr._1
```

instead of the previous one, because the `srcAttr._1` and `dstAttr._1` are the `colorId` in **Forward-Traversal** phase, as written in the paper.