Added list of methods for autocomplete

Added list of available methods to the PHPDoc section of `Flight` class. Inspired by suggestion: http://stackoverflow.com/a/26628288/1363799

Autocomplete was tested in PHPStorm 8.0.1:

![flight-autocomplete](https://cloud.githubusercontent.com/assets/1920639/4838719/f0f75f8c-5fef-11e4-9c47-997a90473f36.png)