Get the limit GET argument from req

Return 10 by default.

Property definitions

popcorn $ TrackerHandler :: limit
	# Get the `limit` GET argument from `req`
	#
	# Return `10` by default.
	fun limit(req: HttpRequest): Int do return req.int_arg("limit") or else 10
lib/popcorn/pop_tracker.nit:85,2--88,75