## [0.3.1](https://github.com/packsaddle/ruby-natural_number_string/compare/v0.3.0...v0.3.1) (2015-09-26)
Update document.
# [0.3.0](https://github.com/packsaddle/ruby-natural_number_string/compare/v0.2.1...v0.3.0) (2015-09-26)
Drop `#natural_number_string?`.
Use `#positive_integer_string?` or `zero_or_positive_integer_string?`.
### Features
* **natural_number:** natural_number_string? is not clear ([bdd8a4c](https://github.com/packsaddle/ruby-natural_number_string/commit/bdd8a4c))
## [0.2.1](https://github.com/packsaddle/ruby-natural_number_string/compare/v0.2.0...v0.2.1) (2015-09-26)
### Features
* **positive:** add positive_integer_string? ([69ecf8a](https://github.com/packsaddle/ruby-natural_number_string/commit/69ecf8a))
* **zero-or-positive:** add zero_or_positive_integer_string? ([6d3c46b](https://github.com/packsaddle/ruby-natural_number_string/commit/6d3c46b))
# [0.2.0](https://github.com/packsaddle/ruby-natural_number_string/compare/v0.1.0...v0.2.0) (2015-09-26)
### Features
* **natural_number_string:** change api ([5501b2b](https://github.com/packsaddle/ruby-natural_number_string/commit/5501b2b))
# 0.1.0 (2015-09-26)
### Features
* **natural-number:** implement natural number ([49e7dc0](https://github.com/packsaddle/ruby-natural_number_string/commit/49e7dc0))