jeremyevans/ruby-warning: Add custom processing for warnings

ruby-warning adds custom processing for warnings, including the ability to ignore specific warning messages, ignore warnings in specific files/directories, include backtraces with warnings, treat warnings as errors, deduplicate warnings, and add custom handling for all warnings in specific files/directories.

This tool can precisely silence deprecation warnings.

While you should fix deprecations in your application, ruby-warning is handy to silence those warnings that you cannot fix. E.g. when they originate from libraries that you cannot change.