Add Cosmological Theorem Provers

[jonnycomes]

Include an implementation of an algorithm for proving Conway's Cosmological Theorem. Ideally, the algorithm will be flexible enough to prove Cosmological Theorems for other non-standard look and says too.

[jonnycomes]

Added a class Cosmology with a method proof() that implements a proof of Conway's Cosmological Theorem. The proof assumes only the digits 1, 2, and 3. Still need to:

• Update documentation.
• Modify the proof to allow for arbitrary digits

The two items above should be quick. More significant changes could include:

• Improving the proof to get a sharp result (of 24) for the maximum age of an exotic element. For instance, one could implement the second level of Litherland's proof.
• Modify the structure of the Cosmology class so that it can be used for nonstandard look and says.