make "the JSON should have the following" not skip the first assertion

when using the `Then the JSON should have the following`-assertion in cucumber like so:

```
Then the JSON should have the following:
  | string  | "string  |
  | integer | 42       |
```

the first line of the table was interpreted as a table header and skipped. The attached patch fixes that.

I don't really know how to write a proper test for that.