fsharp/FSharp.Data — pull request #655 by nkw (2014-07-30 14:31:27+00:00)
Title: Bug: Http - writeBody called before call to customizeHttpRequest

`writeBody` is called before call to `customizeHttpRequest` and it caused exception in `customizeHttpRequest`.

The details can be found here http://stackoverflow.com/questions/24963466/this-operation-cannot-be-performed-after-the-request-has-been-submitted/24965885#24965885.