remove Rmath dependence

I've created a branch to remove the Rmath dependence. I've done some of the easy distributions, but we're going to need some more special functions before we can finish.

- [ ] Beta
- [ ] Binomial
- [x] Cauchy
- [ ] Chisq
- [ ] FDist
- [ ] Gamma
- [x] Geometric
- [ ] HyperGeometric
- [x] Logistic
- [x] LogNormal
- [ ] NegativeBinomial
- [ ] NoncentralBeta
- [ ] NoncentralChisq
- [ ] NoncentralF
- [ ] NoncentralT
- [x] Normal
- [ ] Poisson
- [ ] TDist
- [x] Uniform
- [x] Weibull