Updated to work with boostrap input-group button

I am using the color picker with a boostrap button within an input-group.  This pull should fix the issues I was having.

Example usage:
```html
<div class="input-group">
    <div class="input-group-addon">Background</div>
    <span class="input-group-addon" colorpicker="rgba"  colorpicker-parent="true" colorpicker-with-input="true"  ng-model="someScopeVar"><i></i></span>
</div>
```