Graphical frontend for IRB

AUTHOR:
  Martin DeMello <martindemello@gmail.com>

LICENSE:
  Same as Ruby's

DEVELOPER NOTES:
* Branched off from fxirb, which is no longer maintained

* Using Tk as the default toolkit now, because it's the only one that installed
  painlessly on ruby 1.9.1
  - Also, the Tk text component is a pleasure to work with

* Design goals: 
  - Separate the toolkit-specific bits into their own files, and
    have an include file `guirb.rb` for the common support code
  - Should be easy to add a frontend for your favourite toolkit
  - Should be easy to use this as the basis of an embeddable irb component in
    an IDE

* Long term goals:
  - Write a UI with better support for multiline commands, either with a
    two-pane view (see [dreampie](http://dreampie.sourceforge.net/) for
    example) or a [mathematica](http://www.wolfram.com/)-style notebook view
  - Write a [drscheme](http://www.plt-scheme.org/)-like IDE with good support
    for loading a program into the REPL, trying out bits of code interactively,
    and moving them into the editing pane when they're perfected