Rfloat access name

I am happy that the Rfloat traits are now structs that allow us to access the f64! However, I'm wondering if the naming could be improved.

For example, I will likely forget why I'm accessing `est` and `stderr` using `.0`. Could this field be named something like `value`?
```
let ci = compute_ci(est.0, stderr.0, ci_level)
```