Mechanisms for identifying clusters in graphs. Where these clusters define disjoint sets of vertices, they may be used to define a `VertexPartition` for more convenient manipulation of the vertex/set relationships. Current clustering algorithms include:

- `BicomponentClusterer`: finds all subsets of vertices for which at least 2 vertices must be removed in order to disconnect the induced subgraphs.
- `EdgeBetweennessClusterer`: identifies vertex clusters by removing the edges of the highest 'betweenness' scores (see the importance/scoring package).
- `VoltageClusterer`: Clusters vertices based on their ranks as calculated by `VoltageRanker`.
- `WeakComponentVertexClusterer`: Clusters vertices based on their membership in weakly connected components of a graph.