```ruby
$:.push File.expand_path("../lib", __FILE__)

# Maintain your gem's version:
require "interapp/version"

# Describe your gem and declare its dependencies:
Gem::Specification.new do |s|
  s.name        = "interapp"
  s.version     = Interapp::VERSION
  s.authors     = ["Ryan Zhou"]
  s.email       = ["github@zhoutong.com"]
  s.homepage    = "https://github.com/zhoutong/interapp"
  s.summary     = "Interapp handles simple and secure inter-app messaging."
  s.description = "Interapp is a mountable Rails engine that handles simple and secure inter-app messaging using public key cryptography."
  s.license     = "MIT"

  s.files = Dir["{app,config,db,lib}/**/*", "MIT-LICENSE", "Rakefile", "README.rdoc"]
  s.test_files = Dir["spec/**/*"]

  s.add_dependency "rails", "~> 4.1.1", '>= 4.1.1'
  s.add_dependency "ecdsa", "~> 1.1.0"
  s.add_dependency "rest-client", "~> 1.7.2"

  s.add_development_dependency 'rspec-rails'
  s.add_development_dependency 'sqlite3'
end
```

Make Rails version dependency more liberal
user
```ruby
$:.push File.expand_path("../lib", __FILE__)

# Maintain your gem's version:
require "interapp/version"

# Describe your gem and declare its dependencies:
Gem::Specification.new do |s|
  s.name        = "interapp"
  s.version     = Interapp::VERSION
  s.authors     = ["Ryan Zhou"]
  s.email       = ["github@zhoutong.com"]
  s.homepage    = "https://github.com/zhoutong/interapp"
  s.summary     = "Interapp handles simple and secure inter-app messaging."
  s.description = "Interapp is a mountable Rails engine that handles simple and secure inter-app messaging using public key cryptography."
  s.license     = "MIT"

  s.files = Dir["{app,config,db,lib}/**/*", "MIT-LICENSE", "Rakefile", "README.rdoc"]
  s.test_files = Dir["spec/**/*"]

  s.add_dependency "rails", '>= 4.1.0'
  s.add_dependency "ecdsa", "~> 1.1.0"
  s.add_dependency "rest-client", "~> 1.7.2"

  s.add_development_dependency 'rspec-rails'
  s.add_development_dependency 'sqlite3'
end
```
assistant