Release: v4.0.0

• Improve algorithm to split window.
  • Split window efficiently & speedy.
  • Make panes specious (Make each panes' size as same as possible).
  • Detects impossible window layout before splitting.
• New feature: -C,--cols options: Number of columns of panes.
• New feature: -R,--rows options: Number of rows of panes.
• New feature: --bulk-cols option: Number of multiple columns for each rows.
• Bugfix: Session could not recovered with Pipe mode (GitHub issue #113)
• Update documents.
• Refactoring.
• Reason for major update: Fundamental changes were made. Especially, updated the algorithm for splitting causes the lost of backward compatibility. If the number of pane is big, the layout of panes is totally different from old version's tmux-xpanes.