Change 2 object methods to class methods

[Nikos Bitoulas]

Hello,

please change these methods

- (BOOL)userHasDeclinedToRate;
- (BOOL)userHasRatedCurrentVersion;

to class methods like this:

+ (BOOL)userHasDeclinedToRate;
+ (BOOL)userHasRatedCurrentVersion;

Otherwise you cannot access them (sharedInstance is private).

[Arash Payan]

Good point. This will have to wait until version 3.x because it's an API change.