Typing

It happens in some part of the codes to have `modules` as local variable and in others part, `modules` came from tables. It was ambigous so I prefer to rename it this way. (Just like in others language, constant are capital cases). Also pep8 say : 
"Constants are usually defined on a module level and written in all capital letters with underscores separating words. Examples include MAX_OVERFLOW and TOTAL."