Added Functionality For Choosing Best Combinations
Added Functionality For Choosing Best Combinations

You can now pass best-combination all of your alts, and your improve
function, and it will pick the best two alts to combine into a single
alt, and will return that alt with the proper branch condition.

jackfirth/herbie,jackfirth/herbie,jackfirth/herbie,jackfirth/herbie,jackfirth/herbie,jackfirth/herbie