feat(Request): Also accept query params from POSTed forms

Fixes #170
feat(Request): Also accept query params from POSTed forms

This patch adds support for merging the body of an
'application/x-www-form-urlencoded' request into the params collection
so they can be queried via get_param & Co.

Credit goes to sorenh for the originaly idea and POC. Thanks Soren!

Partially implements issue #180