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.
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
Merge pull request #1750 from sstadelman/patch-1

Added Notes on findAndUpdate()
Normalize bugs.email, so `npm` will shut up

Stop `npm` from spitting out: 
`npm WARN package.json mongoose@3.8.1-pre bugs.email field must be a string email. Deleted.`
Merge pull request #1769 from refack/patch-1

Normalize bugs.email, so `npm` will shut up
docs; fix Query api exposure
Fix some grammatical issues in the documentation
Improve the grammar where "lets us" was used
Fix Bug: enum validator will fail validation except the first one value