Rails automatically calls the `id` method inside scopes and the variable
name makes more sense if it represents investments instead of the number
of investments.
Before we could have multiple current budgets, as we now only have one
current_budget, some specs broke.
As there is no need to display multiple budgets to Valuators, only the
current budget is necessary, we can remove arrays and assume that only
a single budget, the current budget, is displayed to Valuators
