Close previously opened tag

Ensure: tag = previous.tag

Property definitions

html $ HTMLPage :: close
	# Close previously opened tag
	# Ensure: tag = previous.tag
	fun close(tag: String) do
		if not tag == current.tag then
			print "Error: Trying to close '{tag}', last opened tag was '{current.tag}'."
			abort
		end
		current = stack.pop
	end
lib/html/html.nit:90,2--98,4