Add new default commmit message for Flake8 cleanups

dotfiles/gittum/before.gitconfig

   br = branch
   cm = commit
   cma = commit --amend
+  cmf = !sh -c \
+        'git commit --edit --message=\"$(~/.gittum/bin/findcat msg_flake8)\"'
   cmt = !sh -c \
         'git commit --edit --message=\"$(~/.gittum/bin/findcat msg_typo)\"'
   cmw = !sh -c \

dotfiles/gittum/default/msg_flake8

+Flake8