lgamma is deprecated to logabsgamma

[aminya]

In the Julia 1 branch (#17) or once it is merged,
we should address this.

https://github.com/JuliaMath/SpecialFunctions.jl/blob/master/src/deprecated.jl#L1

[Crown421]

I am not sure how we would do that?
The function that VML provides is lgamma and I don't see nice way and a good reason to force some VML.logabsgamma(a)[1] syntax.
What should be changed is the use of Base.lgamma in the tests, which might require special treatment.

[aminya]

Maybe we can just wrap VML.lgamma in some function to provide VML.logabsgamma(a)[1]

https://github.com/JuliaMath/SpecialFunctions.jl/blob/61f9058fbc3428eb8894a57e4f5a2c0217b3e439/src/gamma.jl#L604

We can have both. There is no reason to deprecate lgamma

[Crown421]

The deprecation warnings in tests have been removed in #60 . I don't see further need for changes here, as we can continue to have IVM.lgamma