fct_lump should let you customize the "Other" string

[earino]

Sometimes when I'm lumping together factors, it would be cool if the "Other" factor told me how many factors it had lumped in. For example "Other (27)" if there were 27 factors that made up the long tail.

It would be cool if we could pass this to other.level like:

fct_lump(buncha_factors, other.level="Other (%n)")