Forward stderr from server to stderr, drop stdout

We don't actually write anything to stdout. Also rename the stdout
option to stderr, since that's where we forward the output.
Don't forward stderr to nil

Fixes #455.
Deprecate the stdout option for Connection
Make Node#text work for svg elements

svg elements don't return to the non standard innerText attribute so
fall back on the standard textContent when innerText is null.

Fixes #437.