revise the comment of SliceIntersect

The implementations of SliceDiff and SliceIntersect are the same.
However, the comments of them are opposite.
The former is (slice1 - slice2) while the latter is (slice2- slice1)

Fixed docs: HasErrors is a method not a variable

revise a comment

If it gets a msg from the buffer chan, it will write the message to
outputs.

 move XsrfToken& CheckXsrfCookie to context

change the memcache to the newest

Update smtp.go (develop branch)

For mail servers that do not require Authentication we must pass NIL for the SendMail parameter 2 (the auth parameter). Otherwise it fails to send the mail.

code style simplify

code style simplify