Changes to performance plotting script

This PR cannot be merged as it is, so just close it... I just wanted you to have a look at the `performance.py` script, I've filtered the data a little bit to ease plotting ;)

Here are some raw preliminary numbers in total seconds, first column is `fastq_screen`, second one is `FACS` for the same dataset:

fastq_scr facs
(...)
2.655941 0.128
2.655941 0.004
2.655941 0.001
0.367831 0.125
0.367831 0.004
0.367831 0.004

Good news are that all numbers in right column are consistently lower than the left column. Not so good news are that the script requires some further filtering and validation, so that might be misleading at this point ;)

@arvestad might be interested in this too ;)