Exception when prompt is set hidden = true

When the prompt schema includes `hidden: true` grunt-init errors with the following:

`tty.setRawMode: Use 'process.stdin.setRawMode()' instead.`

I think this is because grunt-init still uses a version of prompt prior to 0.2.0. tty is deprecated since node 0.8 (http://nodejs.org/api/tty.html#tty_tty_setrawmode_mode). But upgrading to latest prompt causes other errors.

For example:

```
init.process({}, [
{
name: 'user',
message: 'Username'
}, {
name: 'pass',
message: 'Password',
hidden: true
}
], function (err, props) {
......
```