Added getSections() method.

I found that is impossible to get template sections from a View object
so I made it possible. This is good expecially when AJAX comes into
play.
Added renderSections() method.

I found that is impossible to get template sections from a View object
so I made it possible. This is good expecially when AJAX comes into
play.

Since the property 'section' is updated once the View has been rendered,
the correct usage is that:
```php
$view = View::make('pages');
$sections = $view->renderSections();
```
Removed old property.
Removed old code.
Restored comment on render().
Include called class name in ModelNotFoundException
Cleaning.
Merge pull request #2773 from billmn/master

Fixed typo
Remove strtolower(), already done in snake_case()
Merge pull request #2782 from PhiloNL/fix/strtolower-snake-case

Remove strtolower(), already done in snake_case()
Blade blade.compiler separate from engine.
Add mergeCollection, diffCollection and intersectCollection functions with tests
fixed typo
Fix missing variable.
Merge pull request #2787 from sergeizelenyi/patch-1

fixed typo
Implement diff and intersect on Support\Collection
Rename merge, diff and intersect functions to match those on Support\Collection
Allow strict mode config option for MySQL.
Update change log.
Increment version.