Revert "add a background"

This reverts commit 5af8fd906c60f0d6033cb0fbf4ffa7bfcbaebfdb.
Revert "Revert "add a background""

This reverts commit b248d2e0a85ee3abf18172303a1b682d1797cd83.
L tetrominos spawned upside down
Use "The New Tetris" color scheme.
update tests (L upside down)
refactor and test insertTetromino()

Moved this method from Board to SquaresMatrix.
add Tetromino.getRows()

refactored from Board
change background color
getRows() sort was lexicographic instead of numeric
ignore qunit files
add squares texture
set border's color for Internet Explorer