Test Univariate Transformations

Need to test univariate transformations.

**Tests**

* [ ] Input Output Shapes
* [ ] Invertibility (small residuals)
* [ ] Compound transforms (MG)



**Transforms**

* [ ] Univariate Histogram
* [ ] Inverse CDF
* [ ] KDE Transforms
  * [ ] Exact
  * [ ] FFT
  * [ ] KNN