git push heroku masterのエラー

rails tutorial 2 の

$ git push heroku master
でエラー文

ec2-user:/environment/toy_app (master) $ git push heroku master
Counting objects: 92, done.
Compressing objects: 100% (78/78), done.
Writing objects: 100% (92/92), 21.59 KiB | 1005.00 KiB/s, done.
Total 92 (delta 6), reused 0 (delta 0)
remote: Compressing source files... done.
remote: Building source:
remote:
remote: ! Warning: Multiple default buildpacks reported the ability to handle this app. The first buildpack in the list below will be used.
remote: Detected buildpacks: Ruby,Node.js
remote: See https://devcenter.heroku.com/articles/buildpacks#buildpack-detect-order
remote: -----> Ruby app detected
remote: -----> Compiling Ruby/Rails
remote: -----> Using Ruby version: ruby-2.4.4
remote: -----> Installing dependencies using bundler 1.15.2
remote: Running: bundle install --without development:test --path vendor/bundle --binstubs vendor/bundle/bin -j4 --deploymen
remote: Warning: the running version of Bundler (1.15.2) is older than the version that created the lockfile (1.16.3). We suggest you upgrade to the latest version of Bundler by running gem install bundler.
remote: You are trying to install in deployment mode after changing
remote: your Gemfile. Run bundle install elsewhere and add the
remote: updated Gemfile.lock to version control.
remote:
remote: The dependencies in your gemfile changed
remote:
remote: You have added to the Gemfile:
remote: * rails (= 5.1.4)
remote: * puma (= 3.9.1)
remote: * sass-rails (= 5.0.6)
remote: * uglifier (= 3.2.0)
remote: * coffee-rails (= 4.2.2)
remote: * jquery-rails (= 4.3.1)
remote: * turbolinks (= 5.0.1)
remote: * jbuilder (= 2.7.0)
remote: * sqlite3 (= 1.3.13)
remote: * byebug (= 9.0.6)
remote: * web-console (= 3.5.1)
remote: * listen (= 3.1.5)
remote: * spring (= 2.0.2)
remote: * spring-watcher-listen (= 2.0.1)
remote: * pg (= 0.20.0)
remote:
remote: You have deleted from the Gemfile:
remote: * byebug
remote: * capybara (> 2.13)
remote: * coffee-rails (> 4.2)
remote: * jbuilder (> 2.5)
remote: * listen (< 3.2, >= 3.0.5)
remote: * puma (> 3.7)
remote: * rails (> 5.1.4)
remote: * sass-rails (> 5.0)
remote: * selenium-webdriver
remote: * spring
remote: * spring-watcher-listen (> 2.0.0)
remote: * sqlite3
remote: * turbolinks (> 5)
remote: * uglifier (>= 1.3.0)
remote: * web-console (>= 3.3.0)
remote: Bundler Output: Warning: the running version of Bundler (1.15.2) is older than the version that created the lockfile (1.16.3). We suggest you upgrade to the latest version of Bundler by running gem install bundler.
remote: You are trying to install in deployment mode after changing
remote: your Gemfile. Run bundle install elsewhere and add the
remote: updated Gemfile.lock to version control.
remote:
remote: The dependencies in your gemfile changed
remote:
remote: You have added to the Gemfile:
remote: * rails (= 5.1.4)
remote: * puma (= 3.9.1)
remote: * sass-rails (= 5.0.6)
remote: * uglifier (= 3.2.0)
remote: * coffee-rails (= 4.2.2)
remote: * jquery-rails (= 4.3.1)
remote: * turbolinks (= 5.0.1)
remote: * jbuilder (= 2.7.0)
remote: * sqlite3 (= 1.3.13)
remote: * byebug (= 9.0.6)
remote: * web-console (= 3.5.1)
remote: * listen (= 3.1.5)
remote: * spring (= 2.0.2)
remote: * spring-watcher-listen (= 2.0.1)
remote: * pg (= 0.20.0)
remote:
remote: You have deleted from the Gemfile:
remote: * byebug
remote: * capybara (> 2.13)
remote: * coffee-rails (> 4.2)
remote: * jbuilder (> 2.5)
remote: * listen (< 3.2, >= 3.0.5)
remote: * puma (> 3.7)
remote: * rails (> 5.1.4)
remote: * sass-rails (> 5.0)
remote: * selenium-webdriver
remote: * spring
remote: * spring-watcher-listen (> 2.0.0)
remote: * sqlite3
remote: * turbolinks (~> 5)
remote: * uglifier (>= 1.3.0)
remote: * web-console (>= 3.3.0)
remote:
remote: !
remote: ! Failed to install gems via Bundler.
remote: !
remote: ! Push rejected, failed to compile Ruby app.
remote:
remote: ! Push failed
remote: Verifying deploy...
remote:
remote: ! Push rejected to fierce-brushlands-56357.
remote:
To https://git.heroku.com/fierce-brushlands-56357.git
! [remote rejected] master -> master (pre-receive hook declined)
error: failed to push some refs to 'https://git.heroku.com/fierce-brushlands-56357.git'