Updates to View::composer()

It's a common thing to bind the `layout` view instead of giving an array of child views. It's a better usage on most cases.

For example, if `dashboard, profile, update, messages, wall` etc. sub views are all extending the `layouts.account_layout` layout, you can pass `layouts.account_layout` to composer instead of all the pages.

Page specific things has to be binded using `with` method, so it fits the logic of using View Composers. 

Anyway, it would be good if this use is mentioned there as a text, or a note. There may be issues with my sentence, so I would be glad if any native English speaker can check and confirm it.