Revert changes introduced in https://github.com/request/request/pull/1282

Fixes https://github.com/request/request/issues/1309

Reverting back the changes introduced in https://github.com/request/request/pull/1282 more info here https://github.com/request/request/issues/1281

~~For some reason this change brakes the form option when it's object.~~ **See below**

From the docs

> form - when passed an object or a querystring, this sets body to a querystring representation of value, and adds Content-type: application/x-www-form-urlencoded header.

~~No idea why it brakes yet, that's just the fix.~~ I can confirm the bug by running my system tests in https://github.com/simov/purest/blob/master/test/request/post.js