update MongoQueue.php

Some fixes to delete successfully processed jobs on queues.

Add missing phpdoc for $processor

Pass credentials as parameters

As per https://github.com/laravel/framework/commit/83316753bbae495cc2…

- If no user was given an empy user was set resulting in an error

- Reverted the config changes
- The credentials are now added to the MongoDB constructor if they are not already present
- Also fixed failing test by changing method access level

- Adding the credentials via dsn causes problems when the password contains an @ symbol

Fix token expiry issue because of time zone difference

Urlencode mongo password

Fixed broken link to php mongodb installation in README.md