We were computing these functions incorrectly.
I'm not sure what distribution these numbers are, but it isn't the
normal exponential distribution. (We're making the probability of
getting a number of a particular bitlength equal, but the number in
that bitlength thats gets chosen is uniformly chosen)
We weren't using these functions anywhere in our codebase, and they
had a nomenclature error. (There aren't exponentially distributed
integers, instead they would be geometrically distributed)
The godocs fell out of sync with the code here. Additionally we had
warning that these randomness functions weren't for cryptographic
use on every function. However these warnings are confusing, since
there was no implication that they would be secure there, and a
single warning on the actual Rand type would suffice. (This is what
is done in golang's math/rand godoc)
Additionally we indicated that rand.Bytes() was reading OS randomness
but in fact that had been changed.
This commit switches all usage of math/rand to cmn's rand. The only
exceptions are within the random file itself, the tools package, and the
crypto package. In tools you don't want it to lock between the go-routines.
The crypto package doesn't use it so the crypto package have no other
dependencies within tendermint/tendermint for easier portability.
Crypto/rand usage is unadjusted.
Closes#1343
