net: write good package comment

[rsc]

net needs a package comment to explain how simple
the basic API is.  all the methods on TCPConn etc drown it out

[rsc]

Comment 1:

Labels changed: added go1-must.

[bradfitz]

Comment 2:

http://golang.org/cl/5673076

Owner changed to @bradfitz.

[bradfitz]

Comment 3:

This issue was closed by revision 008e64d.

Status changed to Fixed.