rename ari_score adjusted_rand_score

doc/modules/classes.rst

doc/modules/clustering.rst

examples/cluster/plot_adjusted_for_chance_measures.py

examples/cluster/plot_affinity_propagation.py

examples/cluster/plot_dbscan.py

examples/cluster/plot_kmeans_digits.py

examples/document_clustering.py

sklearn/metrics/__init__.py

sklearn/metrics/cluster.py

sklearn/metrics/tests/test_cluster.py