Add install generator and support Rails 3 or 4

lib/generators/swagger_rails/install/install_generator.rb

@@ -0,0 +1,16 @@
+require 'rails/generators'
+
+module SwaggerRails
+
+  class InstallGenerator < Rails::Generators::Base
+    source_root File.expand_path('../templates', __FILE__)
+
+    def add_swagger_json
+      template('swagger.json', 'config/swagger/v1/swagger.json')
+    end
+
+    def add_initializer
+      template('swagger_rails.rb', 'config/initializers/swagger_rails.rb')
+    end
+  end
+end