Remove static assert
Remove static assert

I don't remember what that static assert was for but it's causing trouble on Visual Studio Express so let's nuke it
gerram/astar-algorithm-cpp,justinhj/astar-algorithm-cpp,justinhj/astar-algorithm-cpp,majinjing3/astar-algorithm-cpp,gerram/astar-algorithm-cpp,majinjing3/astar-algorithm-cpp