NodeNumbering.jl documentation

```@contents Pages = ["index.md", "theory.md", "api.md"]

Write package description here.

## Installing and testing package

Installing package goes same way like other packages in julia, i.e.
```julia
julia> Pkg.add("NodeNumbering")

Testing package can be done using Pkg.test, i.e.

julia> Pkg.test("NodeNumbering")