EDAMTest : more explicit info about sandbox option

To reviewer : 
- the message inside EDAMTest talked about URL but there were not any coming under those lines.
- the sandbox option is to be found inside the class itself, quite not a trap, but let's gain a search time

Commit messages :
- EDAMTest : more explicit info about sandbox option inside Client class creation

There's an error here. The code should be :
`$client = new Client(array('token' => $authToken, 'sandbox' => true));`
Could you please fix this ? Thank you

Btw, the constructor uses the sandbox by default. But I agree that it's clearer.

Merci Gautier ;)