fogine/couchbase-odm

`catch` block should be provided for every async operation or group of async operations:

````javascript
    User.create({email: 'example@example.com'}).then(function(user) {
        user.email = 'example2@example.com';
        return user.save();
    }).catch(StorageError, function(err) {
        console.log('An storage error occured while saving user instance, code: ' + err.code);
    }).catch(function(err) {//Always provide at least one "global" catch block
        //
    });
````

Note that CouchbaseODM mirrors storage error codes from official nodejs couchbase sdk.

`Promise.error` should not be used because it handles only asynchronously returned errors:

````javascript
    User.create({email: 'example@example.com'}).then(function(user) {
        throw new Error('test');
    }).error(function(err) { // Don't do that, the Error('test') wont be catched here
        //
    });
````