Installation requires packages not listed in dependencies

[TobyBoyne]

After pip installing entmoot, you then need to separately install either gurobipy or pyomo. I think this is good, as it allows the user the choice of which optimiser to use.

However, if you do not install both pyomo and gurobipy, the code throws errors. Therefore, either both of these packages should be included in the project dependencies, or the code should not error when running without installing both of these libraries.