split main.vala into main and tictactoe.vala
add tictactoe vala file to makefile
rename application class from tictactoe to application
simplify main vala code
change makefile to use all aval files in src folder
rename tictactoe.vala to application.vala
move tic tac toe related stuff to own class and set request size of buttons instead of window
override rendering of clicked button