Revert custom key to default

The key 'SDPHP!!!', while appropriate, is no more secure than 'YourSecretKey!!!',
Furthermore changing this key to something besides the default prevents the generation of
a secure key. See https://github.com/laravel/framework/blob/master/src/Illuminate/Foundation/Console/KeyGenerateCommand.php#L45
Merge pull request #44 from Kindari/appkey

Revert custom key to default