Added Notes on findAndUpdate()

Added note to clarify that pre and post middleware is not fired for findOneAndUpdate() class of methods--and this is by design.
release 3.8.0
update stable docs version
docs; fix return description
docs; hide internal method
website; update previous releases
website; add 3.8 release notes link
now working on 3.8.1
Update release-items.md
Update release-items.md
release 3.8.0
update stable docs version
docs; fix return description
docs; hide internal method
website; update previous releases
website; add 3.8 release notes link
now working on 3.8.1
Update version number in README
Merge pull request #1762 from Fodi69/master

Update version number in README
Update README.md