Updated the Readme
Updated the Readme

Removed the 'ObjC only' note.
Added .glyphsPalette explanation.

simoncozens/GlyphsSDK,schriftgestalt/GlyphsSDK,schriftgestalt/GlyphsSDK,simoncozens/GlyphsSDK,simoncozens/GlyphsSDK,simoncozens/GlyphsSDK,schriftgestalt/GlyphsSDK