Read Cirrus CSV files

I wrote a new module called `aio.py` for input/output for acoustics but in this first stage I've only added support for reading csv files generated with NoiseTools software for Cirrus sound level meters.

I've done several tests for some types of csvs (there are more) and it works great. The `test_aio.py` file contains a tricky part to create the filenames of 124 files added in `data/cirrus` folder. All csvs files have been extracted manually from NoiseTools.

I have a .mtp file (zipped file for NoiseTools) for all test data if someone is interested.