Bump to rails 5 in gemspec

factory_bot_rails 6 will not support rails 4.2

Author: composerinteralia

Gemfile.lock

@@ -3,7 +3,7 @@ PATH
   specs:
     factory_bot_rails (5.1.1)
       factory_bot (~> 5.1.0)
-      railties (>= 4.2.0)
+      railties (>= 5.0.0)
 
 GEM
   remote: https://rubygems.org/

factory_bot_rails.gemspec

@@ -5,15 +5,15 @@ Gem::Specification.new do |s|
   s.email       = "jferris@thoughtbot.com"
   s.homepage    = "https://github.com/thoughtbot/factory_bot_rails"
   s.summary     = "factory_bot_rails provides integration between "\
-                  "factory_bot and rails 4.2 or newer"
+                  "factory_bot and rails 5.0 or newer"
   s.description = "factory_bot_rails provides integration between "\
-                  "factory_bot and rails 4.2 or newer"
+                  "factory_bot and rails 5.0 or newer"
 
   s.files = Dir["lib/**/*"] + %w[CONTRIBUTING.md LICENSE NEWS.md README.md]
   s.require_paths = ["lib"]
   s.executables   = []
   s.license       = "MIT"
 
   s.add_runtime_dependency("factory_bot", "~> 5.1.0")
-  s.add_runtime_dependency("railties", ">= 4.2.0")
+  s.add_runtime_dependency("railties", ">= 5.0.0")
 end