```ruby
lib = File.expand_path("../lib", __FILE__)
$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
require "rapa/version"

Gem::Specification.new do |spec|
  spec.name          = "rapa"
  spec.version       = Rapa::VERSION
  spec.authors       = ["Ryo Nakamura"]
  spec.email         = ["r7kamura@gmail.com"]
  spec.summary       = "An API client library for Amazon Product Advertising API, written in Ruby."
  spec.homepage      = "https://github.com/r7kamura/rapa"
  spec.license       = "MIT"

  spec.require_paths = ["lib"]

  spec.add_development_dependency "bundler", "~> 1.14"
  spec.add_development_dependency "rake", "~> 10.0"
  spec.add_development_dependency "rspec", "~> 3.0"
end
```

Use bundler 1.13 or later
user
```ruby
lib = File.expand_path("../lib", __FILE__)
$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
require "rapa/version"

Gem::Specification.new do |spec|
  spec.name          = "rapa"
  spec.version       = Rapa::VERSION
  spec.authors       = ["Ryo Nakamura"]
  spec.email         = ["r7kamura@gmail.com"]
  spec.summary       = "An API client library for Amazon Product Advertising API, written in Ruby."
  spec.homepage      = "https://github.com/r7kamura/rapa"
  spec.license       = "MIT"

  spec.require_paths = ["lib"]

  spec.add_development_dependency "bundler", "~> 1.13"
  spec.add_development_dependency "rake", "~> 10.0"
  spec.add_development_dependency "rspec", "~> 3.0"
end
```
assistant