Minor: use n.times instead of 1.upto(n)

When n is not used in the block, no impact (otherwise starts at 0)
stone_to_text alternative = color_to_char
Comments only
More refactoring about text methods

stone_to_text is gone.
image? uses the more clever to_text (which replaced _to_console)
One more test for filling - empty zone detection
new: Empty zones & bootstrap for score counting.

Last commit in this version. File will be renamed board_analyser.
Cosmetic
stone_to_text renamed color_to_char
One more link for classic 9x9 with 2 players
New GUI features. Mostly score and ending.

Game ending logic added with score count and proposal.
Generic question can be asked in Web GUI.
A series of moves can be loaded from GUI.
Handicap showed in history list.
History display format changed so it can be directly copy-pasted.
Some clean-up/refact about pass and resign commands.
End score proposal + refact.
Command line options for console game.

A series of moves can be loaded from command line.
Feature: prisoner count
Minor change for sentinel group
Cosmetic
Renamed util.rb into board_analyser.rb

Updated test too