Merge pull request #1 from kilburn/affinity

Small improvements to AffinityPropagation (see individual commits)
moved AffinityPropagation to a clustering package.
Extracted AffinityPropagation inner classes.
Do not send messages if they don't change over epsilon.
Merge branch 'affinity' of https://github.com/tonipenya/okapi into affinity
Test changes to try to identify what is going wrong