Add kurtosis and skewness

[andy-esch]

Adding these measures as they could be used in pecan analysis

To do: still need to add tests

[rochoa]

Hey @ohasselblad, it would be nice if you add some tests for these functions.

[andy-esch]

ok @rochoa added them, but the functions aren't being found in the test. It must be in my naming convention. Should I not be bundling in functions that do two different things in one file?

[rochoa]

I did a couple of changes:

• fix the symlink: that was preventing to make the functions available during tests
• raise the min messages to not validate notices

[rochoa]

Can we test with a lower range? Testing with such a big one means the test is very slow.

What is the minimum range we can use to validate these functions?

[andy-esch]

👍 thanks for all the input, @rochoa :)