Base64 fallback on previous OS X versions

[indragiek]

Just realized that -[NSData initWithBase64Encoding] is only available on OS X 10.9. There are many apps that still require OS X 10.7+ compatibility, so there needs to be a fallback of some kind. One way is to include a base64 decoder in INAppStoreWindow.m from one of the many open source implementations out there. Another option is to fall back to using the old drawing method when running on anything lower than 10.9. I'm leaning towards the former.

/cc @jakepetroules

[jakepetroules]

So, the method I used is only available in the 10.9 SDK but is available in the runtime from 10.6. And is deprecated. Suggested solution: duplicate the forward declaration. Simple but effective.

[indragiek]

@jakepetroules Is that documented anywhere?

[jakepetroules]

Yes, in the comments next to the method in the corresponding system header file.

Also, in the signature of the NS_AVAILABLE macro annotating the method.

[indragiek]

👍 I'll push that change tomorrow.

[jakepetroules]

Please release a v1.5 on CocoaPods soon too! :)

[indragiek]

After closing this and figuring out whats up with #162 that sounds like a good time to tag a new release.