raise a RuntimeError

root can always read/write file

fix problem du to new pysam api
- fix requirements
adopt more pythonic architecture
- scripts are in lib subdirectory, with a console_entry in setup
- tests are not anymore in nested treefile, test can be run from setup
- update copyright
- documentation
- use 2 files to set requirements and reqirements for developers

some images have some sghtdiifrence with the reference
due some rounding value when use log on so on
so I compute a basic distnce between 2 images and allow a delta