Add clustering algorithms

[maxkfranz]

Merge the following (unpublished to npm) extensions to the main lib:

• Markov clustering
• K-means set of algorithms
• Hierarchical
• Affinity propagation

For each:

• Review code
  • High-level review for more obvious issues
  • In-depth review
• Merge source
• Merge tests
• Port readme docs to main lib docs

[maxkfranz]

Fuzzy c-means has an issue that is erratic: https://travis-ci.org/cytoscape/cytoscape.js/jobs/300396692