Add iterator support to Attributes

The current Attributes class has no option to retrieve a list of the tags. An option to retrieve these tags would make it easier to use/iterate over the attributes.
Possible solutions:

• Add iterator support to Attributes (ie: Iterator<Attribute> Attributes.iterator(), with Attribute exposing the tag and value)
• Provide a method to retrieve an array of tags (ie: String[] Attributes.getTags())