Rename Scores into Score

Constructor names should always be in singular
Replace level.scores with level.player.score

Score belongs to players, not levels.
This change means that score can be persisted across levels
Refactor Highscore to fix sorting bug

Push score into highscore immediately when game begins
Also set htmlClass = 'current' to it
Undefine htmlClass on every other score in highscore

Add Highscore#sort() which sorts the highscore
Add Highscore#take(n) which returns the topmost n scores

Notera att jag har ändrat på sorteringen för att fixa en sorteringsbugg.
```javascript
// Före
list.sort(function(a, b) {
    return a.total < b.total;
}
// Efter
list.sort(function(a, b) {
    return b.total - a.total;
});
```
Numerisk sortering måste skrivas som `b - a`, det fungerar inte med `a < b`
Merge pull request #43 from scmx/refactor-scores-into-score

Refactor scores into score