Definition
	  Accept-Language = "Accept-Language" ":"
                        1#( language-range [ ";" "q" "=" qvalue ] )
   	  language-range  = ( ( 1*8ALPHA *( "-" 1*8ALPHA ) ) | "*" )

For example, 
the language range ('en-* ;q=0.5') would get parsed into:
 ('en', '*', {'q', '0.5'})