let the user give an 'ignored_files' option for the checkers
Add ignored_files options to all lexicals and reviews
(excepting remove_unused_methods_in_models_review and remove_unused_methods_in_controllers_review: wip)
Add ignored_files option to README.md
Merge pull request #187 from lucaspinto/create_ignore_files_option

let the user give an 'ignored_files' option for the checkers