Update to Inquirer

Fixes https://github.com/yeoman/yeoman/issues/1104

The `prompt` dependency has a dependency on `utile`, which has changed their API, causing an error:

```
/usr/local/lib/node_modules/yo/node_modules/insight/node_modules/prompt/lib/prompt.js:12
capitalize = utile.inflect.capitalize,
^
TypeError: Cannot read property 'capitalize' of undefined
at Object. (/usr/local/lib/node_modules/yo/node_modules/insight/node_modules/prompt/lib/prompt.js:12:31)
at Module._compile (module.js:456:26)
at Object.Module._extensions..js (module.js:474:10)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:312:12)
at Module.require (module.js:364:17)
at require (module.js:380:17)
at Object. (/usr/local/lib/node_modules/yo/node_modules/insight/lib/insight.js:7:14)
at Module._compile (module.js:456:26)
at Object.Module._extensions..js (module.js:474:10)
```