Cherry-pick mode

• Add mn keymap for merging with --no-ff
• Add keymap and conflict-resolving mode for cherry-picking
• Fix a bug where failure to do an operation would mess up the Vim windows

v1.5.0: Introducing the history log buffer

Add the history log buffer(gl from the branch list), which allows:

• Viewing the commit history of a branch
• Viewing information on each commit
• Checking out commits
• Diffing against commits

Other changes:

• Add pr keymap for pull --rebase
• Add q keymap for closing the side-buffers
• Minor typo fixes and output/doc styling changes

v1.4.0: Some new stuff with nothing in common

• Add the rn keymap for renaming branches
• Add a buffer type for rebase-amend
• Add pS command for force pushing branches

v1.3.0: Rebasing functionality and more

• Add the rb keymap to start a rebase.
  • The rebase buffer supports the merge buffer's keymaps(R, <Cr>,
    aa, A).
  • The rebase buffer also support ra to abort the rebase, rc to
    continue to the next patch and rs to skip the current patch.
• Add MerginalToggle command to toggle the merginal buffer.
• Add MerginalClose command to close the merginal buffer.
• Support ps, pl and pf directly on remote branches.
• Fix a bug with non-linear merges that don't have merge conflicts.

v1.2.0: Remote interaction, diffing and more

• Add the mf keymap to run Fugitive's :Gmerge
• Add merginal#branchDetails for better parsing of the branch info
• Add ct and cT for tracking remote branches
• Add ps,pl and pf to push, pull and fetch branches
• Make dd be able to delete remote branches
• bd in the branch list opens the diff files buffer to diff against the
  selected branch.