add options to creation callback

Sometimes I need to create a template which behavior depends on some configurable parameters. To my understanding, the only way to let the template know about such parameters is to create a "proxy" data context:
```javascript
Template.myTemplate({
    context : this, // the original context
    options : {},   // some options
});
```
However, I would rather do something like this:
```javascript
Template.myTemplate(this, options);
```
After that, it would be nice to refer to this `options` in the `created` callback:
```javascript
Template.myTemplate.created = function (options) {
    // ... do somthing or save for later use
    this._options = options;
}
```
This pull request trivially solves the issue, but I'm not entirely sure wheter it complies with your design assumptions.