Matrix madness

• Module props renamed as properties;
• Module coeffs renamed as coefficients;
• Class CoeffLib renamed as CoefficientLibrary;
• Added docstrings to all functions in coefficients module;
• Added matrix module with alternative, matrix-based Pitzer model implementation;
• Added none function to jfuncs module to ignore unsymmetrical mixing;
• Fixed A_ϕ bug in CoefficientLibrary method print_coeffs;
• In preparation for equilibration calculations:
  • Added gettots function to io module.