Add __str__ method
Fix name of generator
Support to_s
Add toString method
Use MessageStringGenerator
Fix test for toString
Reformat generated java code
Fix license sentences
Merge pull request #433 from gintenlabo/fix-licenses

Fix license sentences (#429)
Merge pull request #431 from unnonouno/feature/python-str

Add __str__ methods to user defined objects
Merge pull request #432 from unnonouno/feature/ruby-str

Support to_s in ruby client
Fix command line description: refs #222
Let classifier_base access storage via mixable model
Make member variables of classifier_base private
Make get_storage() public.

Because we want to use it from driver.
Remove mixable model of classifier from driver.
Remove unnecessary comment
Let nearest_neighbor_base have a table through a mixable
Change the argument type from pointer to reference
Let driver use a mixable table in nearest_neighbor_base