Documented and tested version

composipy is simpler and more robust!
Documentation added.
Validation tests added.
Rayleigh Ritz method for buckling calculation has been removed for simplification purposes. But it can be founded in realease 0.1.3.

Test version

• Ply instances to calculate a lamina macromechanical behavior
• Laminate instances to perform laminate calculation
• buckling_load function that calculates the critical buckling load of a composite plate