Misc changes

[sigmike]

• Verifiy trans_id validity
• Renamed certificat to certificate (with backward compatibility)
• Added missing vads_return_mode instance variable
• Fixed incorrect handling of overriden values in instance methods (for example if a value was both in class and instance attributes, it appeared twice in the sorted_array)

[Sylvain]

Nice work Michaël! I just merged a refactoring of the gem and added some specs. Let me know what you think ;)

[lpenou]

\o/

[nakhli]

Hi @Sylvain - you said that this branch was merged, but it doesn't seem to be the case on github. Does that mean that the gem is not in sync with the github repo?
What is the status of the project?