Fix acceptance test for under rails 5.1

[Sixeight]

before	after

Why

• Acceptance test is failed with under Rails 5.1.0 because the Gemfile has multiple gem 'sqlite3' line.
• But the test replace only one line of gem 'sqlite3' for gems.rb changing test.

What

• Ensure 1 line of gem 'sqlite3' . ( commit )
• Use gsub to comment out gem sqlite3' .

Other fails

• LoadError: cannot load such file -- bump/tasks
  • Meregd 🎉 fix at Revert "Start server process in dir where cmd was called" #629
• not acceptance test
  • sprockets requires Ruby version >= 2.5.0. The current ruby version is 2.4.6.354.
    • Officially support Ruby 2.4.x ?
  • ArgumentError: wrong number of arguments (given 2, expected 1) (here)
    • Keyword arguments are now separated from positional arguments on Ruby 3
    • FileUtils.touch cannot accept Hash as optional argument.

Related

• If remove support for old Rails versions, this PR should be ignored.
  • Remove support for old Rails versions #617

Fixes #614

[Sixeight]

merged 🎉
#617