Add option to skip validation when saving new model

Previously, if a _new_ instance of a model calls `save({ validate: false }`, validation still occurred because it was calling `Model.create`. 

I've added the ability to pass the option to validate to the Model.create via the `data` parameter.

For example:

    var p = new Person();
    p.validatesPresenceOf('name');
    p.isValid().should.be.false;
    p.isNewRecord().should.be.true;
    p.save({ validate: false }, function (err) {
        should.not.exist(err);
        p.isNewRecord().should.be.false;
    });

I included the test for this case as well.

P.S. I know passing the data into the `data` parameter looks odd when it is then set via `data = data.data;`, but I couldn't think of a better name and didn't want to rename the existing parameter. Ideas are welcome.