delete old benchmark.py
_splat.c: add splat_gen_ref as reference for benchmark

Add _splat.gen_ref to generate a signal in a fragment
mainly for benchmark purposes to compare the time it
takes to perform other operations relatively.
_splat.c: fix memory leaks with missing Py_DECREF
add bm.py to run complete benchmark
Merge pull request #6 from verdigris/benchmark

Add benchmark