Fix filename that gets generated from dbe:migrations

Hey,

php artisan dbe:migrations --ignore="table1,table2"

The filename is wrong when the file is generated:
./app/database/migrations/2014_08_04_223950_create_mysite_database.php2014_08_04_223950_create_mysite_database.php

The expected result is:
./app/database/migrations/2014_08_04_223950_create_mysite_database.php

This pull request fixes it.
Thanks