TODO:
High Priority:

    - Finish refactoring code into OO form
    

Medium Priority:
    - Allow changing of plot parameters
    - Implement data series as classes and objects
    - Implement Bar and Histogram charts
    - Enhance conformity with English terminology
    - Create more graphic elements (axis titles, etc...)
    - Create a python egg and setup-tools style install
    - Allow different combinations of line, dot, area plots for linear series
    - add pseudo_3D effects

Low Priority:
    - Split or organize tests.py into a test suite
