completed:
    - while loops
    - subs (functions)
    - add return to functions
    - add break
    - add continue
    - allow functions parameters to be passed in
    - create sub return values
    - make local variables that delete after the function finishes
    - add math module
    - import
    - selective importing

incompleted:
    - books (objects)
    - items (arrays)
    - add else if to if statments
    - add try catch
    - fix close square bracket not being allowed in open indentation
