add railties as the runtime dependency (#106)

Author: BenMorganMY

inertia_rails.gemspec

@@ -25,7 +25,7 @@ Gem::Specification.new do |spec|
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
 
-  spec.add_runtime_dependency "rails", '>= 5'
+  spec.add_runtime_dependency "railties", '>= 5'
 
   spec.add_development_dependency "bundler", "~> 2.0"
   spec.add_development_dependency "rake", "~> 13.0"