Benchmarks now with python 3

[lasofivec]

Updated the benchmark script: benchmarks/calc_signal_benchmark.py
so that it works with python 3, plus it reads/writes better into files.

The benchmarks are also no longer packaged

[pep8speaks]

Hello @lasofivec! Thanks for opening this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file benchmarks/calc_signal_benchmark.py:

Line 157:49: E228 missing whitespace around modulo operator
Line 157:60: E231 missing whitespace after ','
Line 163:36: E231 missing whitespace after ','
Line 167:36: E231 missing whitespace after ','
Line 358:38: E228 missing whitespace around modulo operator
Line 361:44: E228 missing whitespace around modulo operator

[lasofivec]

Not sure how, but I did the wrong merge at some point i'm just going to close this PR