RestContext headers doesn't work

[jskarpe]

Behat\Mink\Driver\BrowserKitDriver.php is only passing headers to the client in the visit() method on line 158. When RestContext is bypassing the visit() method (in order to set POST method for instance), then the headers are never passed to the client, thus submitting POST with default headers.

Example: iSendARequestToWithBody

Given I add "Content-Type" header equal to "application/json"
When I send a "POST" request to "api.json" with body:

Actual sent header in this scenario:

Content-Type: application/x-www-form-urlencoded

[sanpii]

See #119 (comment)