Stops parsing summary too early

If I have a summary like this

```
. link:/articles/greetings.adoc[Greetings]
. The beginning
.. link:/articles/01.adoc[The great journey]
.. link:/articles/02.adoc[The home coming]
```

The gitbook init command will report success, but it will only parse greetings.adoc and discards all the remaining articles.
