Fix output buffering levels

Since a recent version of PHPunit (4.1 or 4.2, not sure), you get a warning that your tests are risky if output buffers are not closed properly. This seems to be the case for framework code. The added test will yield the following output without the fixes:

```
$ phpunit -vvv tests/View/ViewFactoryTest.php
PHPUnit 4.4-dev by Sebastian Bergmann.

Configuration read from /home/vagrant/web/pkg/laravel-framework/phpunit.xml

............................R

Time: 587 ms, Memory: 7.50Mb

There was 1 risky test:

1) ViewFactoryTest::testExceptionsInSectionsAreThrown
Test code or tested code did not (only) close its own output buffers

OK, but incomplete, skipped, or risky tests!
Tests: 29, Assertions: 36, Risky: 1.
```