Summary: Render mechanism and theme system

UX/UI

• New color scheme: 256, as the default color scheme. It works well with all 256-color terminal emulators.
• New color scheme: deep-space. It's a 24-bit color scheme.
• UX change: swap positions of default panels:

    Source    | Backtrace
    Variables | Threads
  

• New narrow layout, which consists of source and variables only. Useful when running tests.
• Add aliases to common commands

Bug fixes

• https://github.com/nguyenquangminh0711/ruby_jard/issues/2
• Fix display bug that some rows are out of screen if above rows have word wraps.

Internal Refactoring

• New rendering mechanism, that supports data windowing, selection locating, and cursor.
• Improve compatibility, and add fallbacks in case io/console, or tput are not available.