Simplify net.SplitHostPort handling
Simplify net.SplitHostPort handling

Previously we looked for the request header `X-Appengine-Remote-Addr`.
This is present in the App Engine dev server, but not in the live
system.

Rather than checking for a header, simply make an assumption that if
`SplitHostPort()` failed, we'll just use the `RemoteAddr` as is.

jamesog/ip.jog.li