git-gl and other fzf goodness

[Notgnoshi]

Add interactive git-tags and git-bl browsers. Defer to git-gl for FZF preview for each.

Add heuristics to decide when to add <ctrl-r> rebase or <ctrl-p> cherry-pick keybinds. Add heuristics to decide when (and which branches) to display in addition to the selected branch(es).

Closes #69 Closes #93 Closes #94

• [x] Fix git-blame for fugitive.vim with ignoreRevs
• [x] Fix git-gl errexit and pipefail
• [x] #93
• [x] #94
• [x] Fuzzy git-branch
  • [x] Preview: Show git-log --graph for https://stackoverflow.com/questions/28666357/how-to-get-default-git-branch and selected branch
  • [x] <enter>: Invoke git-gl
  • [x] <ctrl-enter>: switch
  • [x] <delete>: delete
  • [x] <ctrl-m>: merge
  • [x] sort by -committerdate
  • [x] <ctrl-p>: pull
• [x] Fuzzy git-tags
  • [x] <delete>: delete
  • [x] <enter>: Invoke git-gl
  • [x] <ctrl-enter>: checkout