Revert changes introduced in https://github.com/request/request/pull/1282
For some reason this change brakes the form option when it's object
Add application/x-www-form-urlencoded test where -
`form` is object, and `json` is set to `true`
Example:
{form: {some: 'url', encoded: 'data'}, json: true}
Disable body stringify in json method on -
application/x-www-form-urlencoded requests
as they have their body already stringified as url encoded string
inside the `form` method
Merge pull request #1310 from simov/fix-form-option

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