Major Description
Currently partitioning will write a key/value pair for each vertex/adjacent mapping.
This results in heavy IO writes which actually bloats the file and let the partitioning take unnecessarily long.
We should partition directly into the vertex classes and implement a vertex list/array writable which just writes a single key/value pair for a vertex/all-adjacents mapping.
In fact we should make it generic, passing a vertex class which should implement the Writable interface.
