Feature Request : Let ?rankup take the actual uncompleted Katas of a user into account

When using `?rankup`, the bot calculates the number of Katas left to do, without taking the actual number of uncompleted Katas left for a user into account, which makes the bot's advice not very practical. This is especially true for the higher level Katas, as there are far fewer of them.

Please add this as a feature.