Ranger bookmarks should be case-aware

[ngoonee]

Currently it's not possible to have one bookmark to 'd' and another to 'D', as with rangerfm.

[2ynn]

@ngoonee it doesn't look like an issue with ranger.el per se, I think this shoud work:

        (with-eval-after-load 'ranger
          (setq bookmarks-completion-ignore-case nil))

see bookmark-get-bookmark implementation in bookmarks.el