more minimal examples

[shimwell]

In the readme examples I think loc and color are not used

perhaps best to remove these two to make the example quicker for people to understand

I also corrected the import package name as it had the old package name and I removed an argument that otherwise raises an error in the gmsh.write function

[jmwright]

@shimwell Thanks. Is this finished and ready for review?

[shimwell]

Thanks yes this is ready for review

[jmwright]

Thanks @shimwell !