parallel random graph generation
Merge pull request #67 from szymonm/ParalellGraphGeneration

Paralell graph generation
Generic, specizalized version of Node(Re)Numberer
SequentailNodeNumbererSpec
RenumberedGraph fix
Merge pull request #69 from szymonm/GenericNodeNumberer

Generic, specialized version of Node(Re)Numberer to allow supporting supplied node ids that could be Long or any other type. Internally, they are converted to be consecutive ints.