Inconsistent return types for extract_keywords depening on dedupLim

[guilhermelowa]

When the dedupLim is below 1, the function extract_keywords(text) returns tuples in the format: (, )

When the dedupLim is 1, the same function returns tuples in the format: (, ).

This is very confusing. Especially problematic if you're testing multiple values of dedupLim in a loop.