Avoid spring to be bundled

bundle exec rails new ./tmp/example_app --no-rc --skip-javascript --skip-bootsnap --skip-sprockets --skip-git --skip-test-unit --skip-listen --skip-bundle --template=example_app_generator/generate_app.rb

    Gem::RuntimeRequirementNotMetError: spring requires Ruby version >= 2.4.0. The current ruby version is 2.3.0.
    An error occurred while installing spring (2.1.0), and Bundler cannot continue.

Author: pirj

Rakefile

@@ -60,7 +60,7 @@ namespace :generate do
 
       # Rails 4 cannot use a `rails` binstub generated by Bundler
       sh "rm -f #{bindir}/rails"
-      sh "bundle exec rails new ./tmp/example_app --no-rc --skip-javascript --skip-bootsnap --skip-sprockets --skip-git --skip-test-unit --skip-listen --skip-bundle --template=example_app_generator/generate_app.rb"
+      sh "bundle exec rails new ./tmp/example_app --no-rc --skip-javascript --skip-bootsnap --skip-sprockets --skip-spring --skip-git --skip-test-unit --skip-listen --skip-bundle --template=example_app_generator/generate_app.rb"
 
       in_example_app do
         sh "./travis_retry_bundle_install.sh 2>&1"
@@ -183,7 +183,7 @@ namespace :no_active_record do
 
         # Rails 4 cannot use a `rails` binstub generated by Bundler
         sh "rm -f #{bindir}/rails"
-        sh "bundle exec rails new #{example_app_dir} --no-rc --skip-active-record --skip-javascript --skip-bootsnap --skip-sprockets --skip-git --skip-test-unit --skip-listen --skip-bundle --template=example_app_generator/generate_app.rb"
+        sh "bundle exec rails new #{example_app_dir} --no-rc --skip-active-record --skip-javascript --skip-bootsnap --skip-sprockets --skip-spring --skip-git --skip-test-unit --skip-listen --skip-bundle --template=example_app_generator/generate_app.rb"
 
         in_example_app(:app_dir => example_app_dir) do
           sh "./travis_retry_bundle_install.sh 2>&1"