Merge tag '0.3.0' into develop

0.3.0
TODO updated.
TODO updated.
Minor format fix.
TODO list updated.
TODO updated.
Add yard:list_undoc task.
Check more files with RuboCop.
Add utf-8 encoding comments (rubocop).
TODO updated.
Reviewed Method Access Control.
Merge pull request #17 from shun159/develop

Reviewed Method Access Control.
TODO updated.
Merge remote-tracking branch 'origin/develop' into develop
Use earlier version of Rubygems to avoid Bundler fatal error.
Update outdated gem bundle.
Fix rubocop warning.
Merge pull request #19 from trema/feature/update_bundle

Feature/update bundle
TODO updated.
Bindata updated.