r.randi is undefined, should be r.rand

It looks like a typo.  Our class has no method `r.randi`.  I'm assuming the footnote is wrong, rather than the code.

The code being wrong is also a possibility (considering `rand` would be the exception to `randf`, `randn`, and `rand2`), but it could point to being the primary function of the class, and the others to be for less frequent usage.