Updates of namespaces and composer.json

* updated used namespaces
* moved example from test to example folder
* introduced composer.example.json
The `dev-master` means always use what's in `master` branch. The `*@dev` on the other hand means use latest stable dev version or use stable version where composer.json minimum stability is set to stable.

So the `*@dev` is better. Better yet you can specify `~1.3@dev,~2.0@dev` (the 1.3 would allow the Behat 2.x to be used and the 2.0 would allow Behat 3.x to be used, theoretically). This way we won't force people to use Behat 3.x if they don't want.