Getting frustrated about having 4 time in a row the same tetromino ?

Wait no further !

This patch implement the seven bag randomizer, pulling a piece out of
the bag each time and filling the bag when it is empty. This allows for
a more uniform distribution on small samples.

At our school, we have plenty of time at the end of mcqs to play tetris
in emacs and this was something I wanted to change for a bit.

This is also my first contribution ever on an open source project.
The code may not be well formatted.