Disable UnusedMethodArgument for abstract methods
add support for :extra_files config whitelist for extra files, update #492
Test support for dotfiles in data-sources

    .htaccess and .htpasswd were not handled by any data-source
fix code and tests
improved documentation and errors for all_files_and_dirs_in
add more tests for all_files_in
remove the default ht files list
fix (local) tests for rubocop and removed defaults
use concat instead of +=
Merge pull request #503 from nanoc/fix-yardoc

Disable UnusedMethodArgument for abstract methods
Merge pull request #498 from nanoc/feature/dotfiles_gh_492

Add dotfiles support
Merge branch 'release-3.7.x'