Mashape/unirest-nodejs — pull request #18 by hatemogi (2014-06-23 19:26:56+00:00)
Title: fix not to touch content_type when posting a buffer

```is(data).a(Object)``` returns true when ```data``` is a Buffer. And previous code is resetting type as ```form``` if the type isn't set to ```json```.

This commit patches to check a Buffer specifically using ```Buffer.isBuffer``` method.