Pep8 changes

I convert all camelCase variable names into lower_case name as specify by PEP8 standard.
One exception is the name of the command line arguments (with argparse). I didn't know if we you put them in camelCase or not. What do you think?

I remove the check ``end > nb_commands`` which is unnecessary when slicing
https://github.com/MarcCote/smartDispatch/compare/PEP8_changes?expand=1#diff-72eca823ccde82a6ec816cc0cc46942aL54