Documentation says to use key instead of apiKey in Sender constructor

[ffleandro]

Documentation says to use key instead of apiKey in Sender constructor.

Example:
Instead of:

var gcmService = new gcm.Sender({
    key: 'GCM_KEY'
});

should be:

var gcmService = new gcm.Sender({
    apiKey: 'GCM_KEY'
});