Add the ability to pass data to the template via the cli options.

Hi Sindre, 

I added the ability to pass data to the template via command line options. This is useful for super simple scaffolding. Like when you have a boilerplate for JS modules and you want to scaffold them with new module names from the command line. 

So that means a Gulpfile setup with this task:

```js
gulp.task('module', function () {
    gulp.src('templates/module.tpl')
        .pipe(template(true))
        .pipe(gulp.dest('js/modules'));
});
```

And calling the task on the cli like this

`gulp module --name="myModuleName"`

Would result with a new module file with the desired module name.

I am not sure if this is too much functionality for this plugin, but after some thinking I think it is the best fit.

What do you think?