Never knew this, but now that I think about it, I don't think I ever ran into a situation where I got 3 of the same pieces in a row in any Tetris game. Makes sense.
I did the same thing, implementing all the guideline rules into my JS version of tetris here: http://simon.lc/tetr.js/
However over the years, even after the guideline was instituted, there have been many different types of randomizers used. Of course, the original having none, and many a long the way having bugs.
Thanks for the tip ;)
Oh, and pull requests are welcome ;)
Of course, you don't HAVE to follow the official guidelines. I just thought it would be fun to compare.
[1] http://tetris.wikia.com/wiki/Random_Generator