Use AbstractArray if JacobianWrapper is provided

[YingboMa]

No description provided.

[ChrisRackauckas]

I think this should be okay. Thoughts @dextorious ?

[YingboMa]

It can avoid allocation for the example that I made in #14 (comment)

julia> DiffEqDiffTools.finite_difference_jacobian!(J, f!, x, Val{:central}, resid, Val{:JacobianWrapper});

julia> @timev DiffEqDiffTools.finite_difference_jacobian!(J, f!, x, Val{:central}, resid, Val{:JacobianWrapper}); # master
  0.000050 seconds (51 allocations: 3.609 KiB)
elapsed time (ns): 50160
bytes allocated:   3696
pool allocs:       51

julia> include("/home/arch/DiffEqDiffTools.jl/src/DiffEqDiffTools.jl")
WARNING: replacing module DiffEqDiffTools
DiffEqDiffTools

julia> DiffEqDiffTools.finite_difference_jacobian!(J, f!, x, Val{:central}, resid, Val{:JacobianWrapper});

julia> @timev DiffEqDiffTools.finite_difference_jacobian!(J, f!, x, Val{:central}, resid, Val{:JacobianWrapper}); # This PR
  0.000013 seconds (14 allocations: 640 bytes)
elapsed time (ns): 12927
bytes allocated:   640
pool allocs:       14

[coveralls]

Coverage remained the same at 43.59% when pulling 6757a5e on YingboMa:master into 1156c83 on JuliaDiffEq:master.

[coveralls]

Coverage remained the same at 43.59% when pulling 6757a5e on YingboMa:master into 1156c83 on JuliaDiffEq:master.

[codecov]

Codecov Report

Merging #15 into master will not change coverage.
The diff coverage is 0%.

@@           Coverage Diff           @@
##           master      #15   +/-   ##
=======================================
  Coverage   34.34%   34.34%           
=======================================
  Files           1        1           
  Lines         198      198           
=======================================
  Hits           68       68           
  Misses        130      130

Impacted Files	Coverage Δ
src/finitediff.jl	34.34% <0%> (ø)	⬆️

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[dextorious]

I think this should be fine. Interesting usage example too.