Use of AbstractArray type

@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 (https://github.com/exanauts/Simplex.jl/issues/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