I have added new method for formatting

Python like string formatting

**format** _.format(string, args) or _.f(string, args)

```javascript
_.format('http://{0}.com', 'foo') // args as string
=> 'http://foo.com'
_.format('http://{0}-{1}.com', ['foo', 'bar']) // args as array
=> 'http://foo-bar.com'
_.format('http://{hostname}.com:{port}', {hostname:'foo', port:3000}) // args as object
=> 'http://foo.com:3000'
```