Skip Spring

This happens in some circumstances:

    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

@@ -63,7 +63,8 @@ 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"
+         "--skip-git --skip-test-unit --skip-listen --skip-bundle --skip-spring " \
+         "--template=example_app_generator/generate_app.rb"
 
       in_example_app do
         sh "./travis_retry_bundle_install.sh 2>&1"
@@ -189,7 +190,8 @@ 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"
+           "--skip-sprockets --skip-git --skip-test-unit --skip-listen --skip-bundle --skip-spring " \
+           "--template=example_app_generator/generate_app.rb"
 
         in_example_app(app_dir: example_app_dir) do
           sh "./travis_retry_bundle_install.sh 2>&1"