Removing trailing whitespace from markdown files

I know this is probably quite picky, however removing trailing whitespace
gives a much cleaner "feel" to a document when one is editing it.
reflect changes
Merge branch 'pr/remove_trailing_whitespace_from_md'
Removing note about _devel_ branch from GitGuide.

The _devel_ branch has been removed, thus this doesn't need to be mentioned
in the guide anymore.
reflect changes
Merge branch 'pr/remove_devel_from_gitguide'
Adding --no-author option to `dzil test` in GitGuide

Instead of making the users run author tests, and thus requiring them to
install more modules than necessary, they can specify the --no-author option
to skip these tests when testing Dancer2.
reflect changes
Merge branch 'pr/missing_dist_ini_test_modules'