Merge branch 'release/0.6.1' into develop
fix typo in recommender API reference (fix #158)
add description of unlearner seed
suggest unlearner in FAQ of anomaly slowdown
unlearner is implemnted from 0.6.0, not 0.6.2
Merge pull request #163 from jubatus/feature/suggest_unlearn_on_anomaly_slowdown

suggest unlearner in FAQ of anomaly slowdown
add description about `optional` of random seed parameter
Merge pull request #162 from jubatus/feature/seed_parameter_of_random_unlearner

add description of unlearner seed
bump version
Merge branch 'release/0.6.2'