Custom Tooltips and Samples

Creates a chart option for custom tooltips
```javascript
customTooltips: false // default
customTooltips: function(tooltip){
    if(!tooltip){
        //hide tooltip
        return;
    }

    //Show custom tooltip
    //tooltip.x,
    //tooltip.y,
    //etc...
}
```

Samples included for pie/doughnut and line chart types.