Add Support for data-dash-attributes

[aegis41]

There is currently no way to add a data- attribute to a selectize helper. Being able to pass in a list of data- attributes and assign them in the template would be very helpful.

Example:

<label>{{labelText}}: {{ember-selectize
    content=fieldOptions
    selection=value
    placeholder="Select Fields"
    multiple=true
    add-value="change"
    remove-value="change"
    data-my-attr=myAttr
    data-selector=selector
}}</label>