LU-factorize without pivoting for inv of Taylor1 matrices

[lbenet]

This PR adds a specialized methods of inv for matrices with Taylor1 coefficients, which avoids pivoting in lu. This is related to recent changes (JuliaLang/julia#32989) in Julia stdlib/LinearAlgebra, which now uses pivoting by default.

Fixes #221

[lbenet]

@KristofferC @andreasnoack Would this be a good solution for #221?

[coveralls]

Coverage decreased (-0.06%) to 93.514% when pulling 0bc4833 on lb/issue221 into b55f183 on master.

[andreasnoack]

I think specializing lu would be better since it's more general.

[lbenet]

Thanks for the advice! Just pushed a new commit doing it.

[lbenet]

@dpsanders Tests are passing, including Julia nightly. Do you agree in merging this?

[dpsanders]

Great, thanks a lot! We should maybe do something similar for interval matrices (although maybe there are other options to consider there).