Switch from Password to Client_Credentials grant type about node-oauth2-server-example

[pedroetb]

You can add or remove grants types at app.js, edit grants property in oauthserver instance:

app.oauth = oauthserver({
	model: require('./model.js'),
	grants: ['password', 'client_credentials'],
	debug: true
});

[vsantoro]

sorry, i meant to add this question in your other repo node-oauth2-server-mongo-example