Fix Half Star Issue

If you set the `half` option to `true` and hover the 1st star at very left edge, you'll end up and litte error message in Dev Console. 

This error was cause by negative number of `score` value. The simple solution is to use [Math.abs](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/abs) function.

![half](https://cloud.githubusercontent.com/assets/534610/5512675/2ca016f6-87f9-11e4-9e65-a375a9a8ed44.jpg)

Plus I added `.idea` directory for those, who use PHPStorm or WebStorm as their IDE to ignore all project specific files.