Add convenience Entity.getFor(Class<? extends Component>) method, as
mentioned in #50 - "New getComponent overload for Entity".
Fix all warnings reported by Eclipse by removing unused imports and
variables, and adding @SuppressWarnings where appropriate.
Implement reccommendations in #50
Merge pull request #51 from SgtCoDFish/master

#50: Add convenience Entity.getFor(Class<? extends Component>) method