magit-show: bugfix

`magit-diff-range' returns a cons cell of atoms.
magit-key-mode-popup-logging: support --no-merges option
Merge pull request #1341 from mgalgs/no-merges

magit-key-mode-popup-logging: support --no-merges option
magit-revert-buffer-hook: run in magit-revert-buffers
Merge remote-tracking branch 'origin/master'