danger-action

update by #7

• add install_path option
• can escape path of Gemfile

update by #4

• format some files
• update using libraries
• do bundle exec danger when has pluginsFile
  • ref: #3
• do not gem install danger when has pluginsFile
• speed up bundle install, using --jobs 4 --retry 3 options
  • ref https://github.com/actions/cache/blob/master/examples.md#ruby---bundler
• add fail_on_stderr_when_danger option, defalut value: false

bug fix