RANKING, NUEVAS CLASES
ventana nivel
conexión entre ventanas

conexión de main a VentanaNivel, VentanaNivel a Tablero
Creatad Custom Casilla Widget
added mouse scroll event handler
fixed typos
fixed typo
defined interface
implemented Stubs
Sudoku field generation is now complete
added Cache
corrected main bug
added documentation
started Documentation
add getAllCasillas funcion
Merge branch 'master' of github.com:luifevas/PySudoku
added new helper function getAllCasillas
ignore files started with . in rootdir