Empty ships could offensively block enemy at game end

[dgets]

It occurred to me, while writing up #29, that instead of just sending the ships to the 4 corners of the halite universe to get out of the shipyard's way, perhaps we could go on the offensive with them. Least offensively we could build a blockade if there are 4 ships, or more, that have already made their drop-offs. On the converse, we could start pursuing and attempting to destroy enemy ships that may be on their way back to their own shipyard or dropoff.

Always fun to get to go on the offensive a little bit...

[dgets]

Don't neglect the fact that there will be 1-3 opposing team shipyards to potentially blockade, not just the 1 that I'm working with in local testing most of the time here.

[dgets]

See #39 & #43.