Support Emoji

+ Changed the range of double wide characters for Emoji. From U+1F000 to U+1FFFD. Ref. http://en.wikipedia.org/wiki/Emoji
+ Using 'Apple Color Emoji' font for rendering emoji with NSFontDescriptor -fontDescriptorByAddingAttributes:
+ Fixed rendering for Surrogate pair chars, CTFontGetGlyphsForCharacters returns 0 for Surrogate high char glyphs