Change method of calculating number of steps at Scenario Outline.

Hi @grosser .

I changed the calculation of the number of steps in scenario outline.

eg:

```feature
# Based on turnip/examples

Feature: Battle a monster
  Scenario: normal monster
    Given there is a monster
     When I attack it
     Then it should die
      And Fanfare

  Scenario Outline: a simple outline
      Given there is a monster with <hp> hitpoints
      When I attack the monster and do <damage> points damage
      Then the monster should be <state>

      Examples:
        | hp   | damage | state   |
        | 10   | 13     | alive   |
        | 8    | 5      | dead    |

  Scenario: strong monster
    Given there is a strong monster
     When I attack it
     Then it should die
      And Fanfare
```

Before calculation, number of steps is **11** (`normal monster` = 4, `a simple outline` = 3, `strong monster` = 4).
(If  `a simple outline` is written at the end of the file, number of steps is **14** ...)