Removed options for the time being, not sure what to do with it. Also changed a bunch of iterators to const_iterator.
Refactored code and broke generating_sets up into smaller functions. Got rid of two unneeded copy-ctor calls. 'Is subset of set' logic now using std::includes from std::algorithm. Changed one function from using indexing calls to iterators instead. I imagine there's a small drop in benchmark execution time.