Swift support

[krunk4ever]

When attempting to use this framework with Swift 3.0, I kept on getting the following error:

let helloWorldText = NSAttributedString(string: "hello world")
NSAttributedString(format: "%@", helloWorldText)

Ambiguous use of 'init'

I had to modify the header following the same pattern that NSString.h uses in order my compilation to work. The pattern is that the pass in locale as a nullable id, instead of nullable NSLocale *

- (instancetype)initWithFormat:(NSString *)format, ... NS_FORMAT_FUNCTION(1,2);
- (instancetype)initWithFormat:(NSString *)format arguments:(va_list)argList NS_FORMAT_FUNCTION(1,0);
- (instancetype)initWithFormat:(NSString *)format locale:(nullable id)locale, ... NS_FORMAT_FUNCTION(1,3);
- (instancetype)initWithFormat:(NSString *)format locale:(nullable id)locale arguments:(va_list)argList NS_FORMAT_FUNCTION

I've also added nullability to your header file as well.

[krunk4ever]

Forgot to mention I added a Swift extension in my project:

extension NSAttributedString {

    /// Allows you to format NSAttributedString the same way as NSString
    /// by passing in a comma separated list of attributed strings after the format
    ///
    /// - Parameters:
    ///   - format: format
    ///   - arguments: comma separated list of NSAttributedString
    convenience init(format: String, _ arguments: CVarArg ...) {
        // this is how to convert an array of CVarArg to a CVaListPointer
        let argList = getVaList(arguments)
        self.init(format: format, arguments: argList)
    }

}

which allows me to called the sample code below:

let helloWorldText = NSAttributedString(string: "hello world")
NSAttributedString(format: "%@", helloWorldText)