Set the document number for the pre-Issaquah mailing.
Specify experimental::fundamentals_v1 in the <optional> synopsis, and omit namespace std elsewhere.

Even the standard doesn't consistently wrap declarations in a namespace, and
it'll be easier to keep the TS consistent if the header synopsis is a single
point of truth for which namespace a name lives in.

This fixes #5.
Remove "optional<T>::" from the signatures of `optional` methods.

The convention in the standard is to infer that a function is a member function
from which section it appears in, rather than by qualifying each signature.