Add inverse lut option #3
General refactoring fixes
Add pre and post lut options #3
Update css
Move cmd line tool to a proper file (fixes #4)
Use argparse to set options (fixes #2) #3
Update readme #3
Merge branch 'feature/add_pre_post_lut' into develop
Remove an obsolete comment
Create ocio_helper module to factorize OCIO code
Merge branch 'feature/OCIO_helper' into develop