Documentation for 5.0.0

[drvinceknight]

With the recent great contributions from @alexhroom, it feels like 5.0.0 might be gaining some lost momentum.

With that in mind I'd like to start thinking about the structure for documentation.

I think that I'd like to take the opportunity of 5.0.0 to strongly follow the diataxis framework and perhaps more strictly than at present:

• Tutorials
• How to guides
• Reference
• Explanations (perhaps an opportunity here to write a lot of theory)

I also think that with the added dimension of games we should aim to think about how that would look essentially something like separating in to either:

• Generic docs
• Game Specific docs

So for example perhaps (and please don't worry too much about the title of the files, more the general framework structure):

docs/
index.rst
|--- tutorials/
     |--- index.rst
     |--- recreating-axelrods-first-tournament.rst   # A walk through tutorial which I realise is IPD specific but nonetheless seems    
     |--- implementing-rock-paper-scissors.rst
sensible
     |--- ipd/
          |--- index.rst
          |--- simulating-speciation.rst  # A walk through tutorial specific to the IPD
     |--- ultimatum_game/
          |--- index.rst
          |--- recreating-the-results-of-<some-paper>.rst  # a guess
|--- how-to-guides/
      |--- index.rst
      |--- how-to-run-a-tournament.rst
      |--- how-to-run-a-moran-process.rst
      |--- how-to-implement-a-new-game.rst
      |--- how-to-implement-a-new-action-set.rst
      |--- how-to-define-a-strategy.rst
      |--- how-to-contribute.rst   # Perhaps more here
      |--- ...
      |--- ipd/
           |--- how-to-write-a-strategy-for-the-ipd.rst
           |--- how-to-fingerprint-an-ipd-strategy.rst
      |--- ultimatum_game/
           |--- how-to-write-a-strategy-for-the-ultimatum-game.rst
           |--- ...
|--- explanations/
     |--- index.rst
     |--- structure-of-the-library.rst
     |--- how-tournaments-are-parallelized.rst
     |--- ...
     |--- ipd/
          |--- how-are-ipd-strategies-implemented.rst
     |--- ultimatum_game/
          |--- how-are-ultimatum-game-strategies-implemented.rst
|--- reference/
     |--- index.rst
     |--- introduction-to-game-theory.rst
     |--- moran-processes.rst
     |--- ipd/
          |--- index.rst
          |--- what-is-the-ipd.rst 
          |--- axelrods-first-tournaments.rst
     |--- ultimatum_game/
          |--- index.rst
     |--- ....

I'd imagine that if/when a new game gets added we'd also include documentation at the minimum in the reference section (giving some background to the game). (Wouldn't reject any other documentation types of course!)

I think the docs/index.rst should include a list of all the implemented games.

Minor: perhaps with sphinx a cool thing can be done where you click on ipd somewhere and get all the ipd type docs that automatically come up in the same diataxis structure...