Adding ChainRules compatibility to FastDifferentiation

[brianguenter]

@gdalle
I think I have figured out how to do this. Am looking through the docs for ChainRules to make sure I understand the details. Where are the rrules and frules for things like SVD, LU, etc. , defined? In the LinearAlgebra package? Flux? Somewhere (maybe several somewheres) else?

I want to use these rules to test the code once I add it to FastDifferentiation.

Never mind, I found the code in the rulesets subdirectory in the ChainRules repo.