Add option to display changelog for the file in which the directive is used.

[tomkivlin]

e.g. instead of having to use a filename_filter, have an option like this_file_only: true or something, and the changelog displayed is just for that file.

This would be handy for displaying the recent changes within each file, without having to manage a load of differnet regex strings across a load of files.

[guideloom]

This! All day this! I came specially to this repo to make this suggestion.. but here it is already :)
BTW; how did you use the filename_filter for this?