bugfix: error in fileaccessor test code

Can only save a TextBuffer, not a plain array.

	modified:   test/fileaccessor.rb
cleanup: separated antsy into 3 files

Moved window, screen, and terminal each into its own file.

	modified:   make_jedi.rb
	modified:   run_jedi.rb
	deleted:    src/antsy.rb
	new file:   src/antsy/screen.rb
	new file:   src/antsy/terminal.rb
	new file:   src/antsy/window.rb
	modified:   src/editor.rb
	modified:   src/filebuffer.rb
bugfix: default history file, so we don't have to specify it on startup

	modified:   src/editor.rb
feature: open an irb session in current binding

This is really nice.  With one keypress, I can drop into an irb session
and hack at the editor code and variables.  This is really nice for
debugging, because I can directly observe what is going on.

	modified:   src/antsy/screen.rb
	modified:   src/editor.rb
	new file:   src/irb.rb
	modified:   src/keymap.rb
bugfix: undo/redo errors at the end of the file.

The issue was: if lines disappeared during and edit, then to try to
recover that change required first moving to the line that the change
occurred on. This was added as a feature some time ago, so the user
could see exactly what was happening durning and undo/redo.  In this
situation, because the cursor can never get to the edited line, the
change was inaccessible. This fix now handles that situation.

I also simplifed undo/redo a little bit.

	modified:   src/bufferhistory.rb
	modified:   src/filebuffer.rb
cleanup: better comments

	modified:   src/bufferhistory.rb
bugfix: fixed some test code errors

More to come...

	modified:   test/bufferhistory.rb
	modified:   test/syntaxcolors.rb
	modified:   test/test.rb
bugfix: handle empty yaml file for histories

Let it return an empty hash.

	modified:   src/histories.rb
cleanup: removed some redundancy and other cleany things

	modified:   src/compatibility.rb
	modified:   src/antsy/screen.rb