Moves tanks from navy to army table

edits the models of the army and navy to be accessible
in the correct places
changes the migrations
changes the schema
changes the seed file to load correctly
Moves economic score to the State model

Better belonging to the state than to the economy
since the economic score is relative to all other states
Refactors data files so Myanmar is standard name
for the former Burma
Abstracts getting top scores all all types to respective models
Refactors Power#calculate_power to be reusable in future 
power calculations as time goes on
Merge pull request #11 from ggw215/power_ranking

Power Score Calculator Refactor