Merge branch 'release/0.5.3'
Fix URLs of 20news
Fix tutorial step to start classifier
Fix a typo
Fix explanation
bump version
Merge branch 'release/0.5.4'
Merge pull request #138 from jubatus/fix-tutorial-step

Fix tutorial step to start classifier
Merge pull request #137 from jubatus/fix-news20-url

Fix URLs of 20news
Merge remote-tracking branch 'origin/master' into develop