Log errors instead of emitting as an error

Firstly, thank you for making this plugin, it's great that someone else is also trying to do this.

If the plugin emits the file as an error, then gulp-phpcs will stop at the first error. Currently this is just logging it with `gutil.log` which could be replaced with other reporting tools.
You do not get the Gulp way. Content of the file can be changed via previous plugins, thus we should check it instead of the original content from the file system.