Passing variables from url placeholders into response content template

From now values under placeholders in url are going to be available in twig template under ``path`` variable. 
If there are no placehodlers ``path`` variable will be an empty array.

Simple example: 

```
# responses.yml
request_with_variables_in_request_path:
  request:
    path: "/users/{email}/tasks/{taskId}"
  response:
    content: "Get task with ID {{path.taskId}} from user with email {{path.email}}"
```

So now after http request on "/users/norbert@coduo.pl/tasks/1" TuTu will return following response:

```
Get task with ID 1 from user with email norbert@coduo.pl
```