change request body function.

* enable status, header setting anywhere.
* deprecate lbs
* add bytes, lazyBytes, text, lazyText, showing, string, char
  request body functions. these function append request body.
* add reset function to reset request body to empty.
fix apiary-purescript lbs deprecated warning.
update cabal, README.md.
update changelog.
Merge branch 'develop'

* you can set status and response headers anywhere.
* deprecate lbs.
* add bytes, lazyBytes(~ lbs), text, lazyText, showing, string, char request body functions. these functions **append** request body.
* add reset function to reset request body to empty.