add ttt_spec.rb to test tic-tac-toe game
add ttt_spec_helper.rb
fill out structure of ttt_spec.rb
update tic-tac-toe

This commit adds the new images for the board/x's/o's and updates
the js files (and adds board-analysis.js).
remove duplicate call to win_or_block() in handle_second_click()
update js files for tic-tac-toe
Merge branch 'ttt-specs'