Docstrings and interface updates

A number of development updates have been added:

• No longer reliant on torch interp1d
• Docstrings added for classes and methods
• Added "Simulator" object to simplify the interface
• Adding "Packed" object to identify how parameters are transported through the simulator
• Kappa grid bug fix
• Coverage tests

0.2.0

All model components inherit from a Parametrized class, which keeps track of the directed acyclic graph underlying them. This enables passing parameters as args lists, kwargs dictionaries or flatten tensors through arbitrary hierarchical models. It also enables easily setting parameters as static (fixed) or dynamic (sampled and passed into the simulator at runtime).