The default fontSize release

What's new?
Fixes a bug from version 0.9.0 where the lineSpacing property would have no effect whatsoever.
Added default fontSize so that labels without specified fontSize will also work as expected.
Removed flakey frame getter.

Output examples:

NORLabelNode *multiLabel = [NORLabelNode labelNodeWithFontNamed:@"Baskerville"];
multiLabel.text = @"Cattle die,\nkinsmen die\nyou yourself die;\nI know one thing\nwhich never dies:\nthe judgment of a dead mans life.";
multiLabel.verticalAlignmentMode = SKLabelVerticalAlignmentModeCenter;
multiLabel.horizontalAlignmentMode = SKLabelHorizontalAlignmentModeCenter;
multiLabel.position = CGPointMake(CGRectGetMidX(self.frame), CGRectGetMidY(self.frame));

Applying changes to the label:

multiLabel.fontColor = [SKColor yellowColor];
multiLabel.fontName = @"Helvetica";

multiLabel.lineSpacing = 2.0;

multiLabel.position = CGPointMake(20, CGRectGetMidY(self.frame));
multiLabel.horizontalAlignmentMode = SKLabelHorizontalAlignmentModeLeft;