16-bit Unicode character support

[kloned]

@jmesnil we've not been able to deal with some unicode characters (especially with cyrillic and romanian).
Solved by replacing %c with %C in [body appendString:[NSString stringWithFormat:@"%c", c]];

String Format Specifiers description: https://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/Strings/Articles/formatSpecifiers.html#//apple_ref/doc/uid/TP40004265-SW1