RFC 4627 is obsoleted

[xuwei-k]

argonaut/argonaut/shared/src/main/scala/argonaut/JsonNumber.scala

Lines 262 to 263 in 8b1e261

	* the grammar in the JSON specification (RFC 4627 -
	* http://www.ietf.org/rfc/rfc4627.txt), section 2.4. If it is valid, then

This document replaces [RFC7159]. [RFC7159] obsoleted [RFC4627],
which originally described JSON and registered the media type
"application/json".

https://tools.ietf.org/html/rfc8259

[seanparsons]

Is there anything we need to action from this?