Added .gitignore file.
Add swap files to .gitignore
Check for stochastic matrix in operations

Make sure that slices which are not stochastic, and products of a
stochastic matrix with a vector or non-stochastic matrix correctly
return a numpy.matrix object, not a stochmatrix.stomat object.
Eliminate import cut_noise

The scitools package is not needed; we do not ever use the cut_noise
function.
Fix multiplication of stochmatrix and reward vect

As of this commit, stochastic matrix multiplication produces correct
output types (not always another stochastic matrix), and
policy_improvement works correctly.
Reduce default tolerance in checking float equality.
Fix solving of ARAT games.

The policy improvement algorithm had a bug such that it would work only
under the assumption that the game was a perfect information game. This
commit also adds a function for generating random ARAT games.
Merge branch 'arat_fix'