Use variable encoding for ints, longs, and doubles in the specialized serializers.

This reduces the amount of data communicated for pagerank by 2 - 3X on the Google graph.

left side is with variable encoding

right side is without

![screen shot 2013-11-12 at 3 10 37 pm](https://f.cloud.github.com/assets/323388/1527313/9a313068-4bf2-11e3-8330-019eadb6552b.png)