Code & performance optimizations

[fdocr]

There are optimization low hanging fruit that could use a refactor and can be worked on with independent PRs for them:

• Move direction constants (i.e. "up", "down", etc)
• BattleSnake::Context currently returns a { moves: X, neighbors: Y } but that could benefit from being handled as a struct or class of its own (utility methods on them)
• Any loop related logic optimization throughout strategies and Strategy::Utils methods
  • Doing a better job with nested loops and heuristic opportunities to iterate more efficiently has lots of potential to improve performance overall