Fixes typo on dynamic call to filterFailsExcept
Returning environment string from detectEnvironment

`app/bootstrap/start.php`'s assignment of the global `$env` is failing because
`detectEnvironment` is no longer returning the environment string it's
supposed to.
Merge pull request #2192 from deefour/bugfix/environment-detection-return

[Bug] detectEnvironment no longer returning environment string
Merge pull request #2191 from deefour/bugfix/filter-typo

[Bug] Typo on dynamic call to filterFailsExcept