Implemented Image#path.

* refer to #252
* fixes #252
* i'm not certain how to write tests for this, but i'm certain it needs some
Ported textcursor from Purple Shoes. Try out the following:

Shoes.app do
  msg = para 'hello ' * 20
  msg.cursor = -1
  keypress do |k|
    n = case k
      when 'ARROW_LEFT'; -1
      when 'ARROW_RIGHT'; 1
      else
        next
    end
    n += msg.cursor
    len = msg.text.length
    n = len unless n > -1
    msg.cursor = n % (len+1)
    gui.flush
  end
end
simple image path test
Merge pull request #277 from hkal/implementing_image_path

Implemented Image#path.
Removed sample31 from the list of working samples for now

* not working on Linux and Mac
* please reference #276
* [skip ci]
Cleaned up the bin directory of swt-shoooes stuff

* now there are only 3 executables: shoes, shoes.bat and ruby-shoes
* done to avoid confusion as to which executable to use
* Adjusted the Rakefile to reflect... as for my understanding the
  check for the Host OS could be removed and I did it... don't
  have shoes on Windows set up yet - @ashbb may you please check
  if running the samples still works?
* adjusted README
* [skip ci]
The current bin/shoes.bat doesn't work on Windows. So, I did the following.

- bring back swt-shooose.bat
- delete the current shoes.bat
- rename the file name from swt-shooose.bat to shoes.bat

Now `C:\tmp\shoes4>bin\shoes samples\simple-sound.rb` works on Windows.
Add three adjusted samples, i.e. expert-irb-adjusted.rb, expert-pong-adjusted.rb and expert-tankspank-adjusted.rb.
Initial attempt to make the 'simple-curve' sample work as an introduction
to Shoes.
Have added a 'Curve' class to lib/shoes and lib/shoes/swt.
This seemed to be the 'simplest' implementation to display an image
matching that on the cairographics samples.

Possible immediate issues:
* Should use Point instead of x1, y1 etc.
* Doesn't calculate the bounds