Replace Underscore.js with Lo-Dash 

I propose to switch from underscore to lo-dash. It is 100% replacement with identical API. General reason is performance.

Here I'm posting results of benchmark running on lodash.com on my idle Macbook in Chrome 23 (V8 as node).

![chrome](https://f.cloud.github.com/assets/295197/36929/be89154c-5388-11e2-8786-8190f7b14cd4.png)