Exemple of usage :
```
        $('table.highchart')
          .on('highchartTable.cleanValue', function(value, options) {
               if (options.indexTr == 0) {
                 options.value = options.value.replace(/\$/, '');
               }
          })
	  .highchartTable()
```

List of options passed to the event :
* value (that's the one that must be changed, contains the value already cleaned by HighchartTable)
* rawValue : the value not cleaned by HighchartTable
* td : jQuery objet of the td were the valued is extracted from
* tr : jQuery objet of the tr where is td is readed from
* indexTr : index of the tr (starts at 0)
* indexTd : index of the td (starts at 1)