Handled EmailReference

This pull request handles the EmailReference pointer message which has been described in #4.
OK, thanks for clarifying. I haven't met any tech stacks myself that did not have tools for working with BASE64 (but some are sure to exist), so I don't think that would be setting the bar too high. For CDATA, there are potential encoding issues (http://en.wikipedia.org/wiki/CDATA#Issues_with_encoding) which makes it less robust to bet on, at least for 'arbitrary' data. I vote for BASE64.