Report redundant configuraiton keys as error
Make configuration into optional
Use converter_config in xxx_serv to report errors
Remove unused method
Merge pull request #489 from unnonouno/feature/config-cast-typo-error

Feature/config cast typo error: fix #488
Fix indent
Add test expect
Merge branch 'fix-jsonconfig' into develop

refs #489
Merge branch 'develop' into feature/optional-configuration

Conflicts:
	jubatus/core/fv_converter/converter_config.cpp
Merge pull request #491 from unnonouno/feature/optional-configuration

Feature/optional configuration: fix #134
Merge remote branch 'origin/develop' into feature/coreset