Add support for mock POST in request

[panthershark]

I did a first pass of this for a router project. Test coverage includes basic form encoded body with fomidable body parser.

Here is working test over in another project. (Need to get similar test in here too)
https://github.com/tommydudebreaux/pipeline-router/blob/master/tests/post.js#L45

We should probably get some tests for other body parser use cases.

[panthershark]

This is old. I stopped supporting pipeline-router.