Added the color option

Browsers that support the placeholder attribute display by default gray text. This change allows users to choose the color they wish :

```
$("input[type=text]").ezpz_hint({
		hintClass: 'myClass',
		hintColor: '#DEDEDE'
});
```

By default the color is `#999999` :
![ezpz_hint_color](https://f.cloud.github.com/assets/1552526/1045360/9971c9ea-1023-11e3-8bec-523a64eb98b0.png)