access status after evaluating response

[joprice]

This addresses #5 by moving the computation of status and content type until after the handler promise has completed, since that promise may have asynchronous mutations to the context that change these fields.

I also added a module statement to the sample Worker to fix an error hit from a build (likely a stricter compiler error in more recent fsharp versions).

[AngelMunoz]

Hey there! thanks for taking a look at this give me a chance to check it over the weekend (or maybe over half the next week) to get it released!

The change makes sense I don't know why I didn't catch this when I was doing it