tidies up nullplayer fucntion
tidies up symmetry
adds extra test to null player
adds test for characteristic function being unordered
removes useless test
sorts the keys in char_fun
replaces show with _repr_
Tweaked _repr_ to be more concise, docs might need checking
makes minor changes to docs
Incorporated _latex_ method
Merge branch '16332' of github.com:theref/sage-game-theory into 16332
converts singular into a one element tuple
Merge branch '16332' of https://github.com/theref/sage-game-theory into 16332
Added more discussion about cooperative game and cf
Merge branch '16332' of github.com:theref/sage-game-theory into 16332
removes payoff_vector and updates docs
makes marginal_contributions hidden
removes useless import
renames a variable
More mathematics added to docs, just about to start on monotone games