Use of AbstractArray type

[kibaekkim]

@frapac and I found this package is interesting. And we have also implemented similar stuffs in https://github.com/exanauts/Simplex.jl/blob/master/src/LP.jl While we are considering to replace our implementation by this package (exanauts/Simplex.jl#19), I have a quick suggestion. I believe Vector type can also be defined as a template, which would allow to use other types such as CuArray. For example, https://github.com/jump-dev/MatrixOptInterface.jl/blob/master/src/matrix_input.jl#L184

[blegat]

Totally agree, we wanted to start simple but that's the long term goal, PR welcome :)