Added return value info to _.times docs.

Previously there was no mention on the home page that **_.times** returns an array of values.

This is important, because **_.times** is costly when you have a large **n** and you are not going to use the returned value.

I also updated the tests for **_.times** to demonstrate a useful recipe where you pass **_.identity** as an argument into **_.times**. This recipe mimics **_.range**, but it is much more adaptable.