Tests: add memory performance tests
Tests: add memory performance tests

A new test file is added which contains memory and CPU tests. For now,
only the memory usage tests work (threading!). They print out tables of
memory usage based on file path and on function. Additionally, they check
some basic measurements: if all packets were processed and if a
collection of version 9/10 called any functions in 10/9.

Refs #24

cooox/python-netflow-v9-softflowd