Implement other sample graph types

[csmangum]

• Small-World Graph
  Description: A graph characterized by short path lengths and high clustering,
  often generated by the Watts-Strogatz model.
  Use Cases: Social network analysis and the study of efficient communication
  networks.
• Multigraph
  Description: A graph where multiple edges (parallel edges) can exist between the
  same set of vertices.
  Use Cases: Transportation networks and network reliability studies.
• Hypergraph
  Description: A generalization of a graph where an edge (called a hyperedge) can
  connect any number of vertices.
  Use Cases: Representing complex relationships in data sets, such as database
  modeling and VLSI design.