Please review

[Bret Jordan <Bret_Jordan@symantec.com>]

We have added suggested text to resolve the following github issues, please review, comment, and improve as needed:

Issue 8: max_content_length example value is not exemplary

https://github.com/oasis-tcs/cti-taxii2/issues/8

Found in two places in 4.2.1

Issue 17: Add text about TLS 1.3 0-rtt

https://github.com/oasis-tcs/cti-taxii2/issues/17

Found in 8.2.2

Issue 19: The X headers are not clear about which date

https://github.com/oasis-tcs/cti-taxii2/issues/19

Found in 3.2 and 5.6.1

Thanks

Bret