Remove debugger gem from example app Gemfile

It's essentially not needed for our test and tend to cause installation problem.

Author: yujinakayama

.travis.yml

@@ -32,13 +32,13 @@ before_script:
 script: "script/run_build 2>&1"
 
 rvm:
+  - 1.9.3
+  - 1.9.2
   - 1.8.7
   - 2.3.0
   - 2.2
   - 2.1
   - 2.0.0
-  - 1.9.3
-  - 1.9.2
 
 env:
   - RAILS_VERSION='~> 4.2.0'

example_app_generator/generate_app.rb

@@ -15,6 +15,7 @@
   # edge branches
   gsub_file 'Gemfile', /^.*\bgem 'rails.*$/, ''
   gsub_file "Gemfile", /.*web-console.*/, ''
+  gsub_file "Gemfile", /.*debugger.*/, ''
 
   if Rails::VERSION::STRING >= '5.0.0'
     append_to_file('Gemfile', "gem 'rails-controller-testing', :git => 'https://github.com/rails/rails-controller-testing'")