Adding failing test for annotated POST payloads.

If the POST payload has any kind of annotation, it is not picked up
by the doclet. This commit adds a regression for this fact.

We discovered this behaviour when trying to annotate a payload with
`@javax.validation.constraints.NotNull`. I did not want to introduce
a new test dependency, so I tried it with other annotations. It does
behave the same way with `@java.lang.Deprecated` as well.
Allow POST payload to be included even if annotated with unknown class.

This fixes the failing test introduced by the previous commit.

The idea is that POST methods are allowed to have one weirdly annotated
parameter, as long as it's not excluded and not JAX-RS.
Remove "body" type parameter check in `shouldIncludeParameter`.

From what I understand, the call was redundant:
- in the original code, it always returned true because it was inside
  a condition of "has no annotations", and `paramTypeOf` will return
  "body" for that condition (also risking NullPointerException if the
  annotations == null)
- in the modified code all the allowed/excluded conditions are tested
  first, leaving only unrecognised annotations in the end, which would
  return "body" from `paramTypeOf` as well.

Therefore, the explicit parameter type checking is unnecessary.
Merge pull request #28 from sldblog/post-payload-fix

Don't exclude POST parameter with unrecognised annotations