toXML methods can generate invalid XML

[ryan-mahoney]

in XML, ampersands and several other characters need to be escaped before they are added to an XML document. For example, if my job title is "Sales & Marketing Director" when the API attempts to send the XML document to the HighriseAPI server, 37signals will return a 500 http status because the XML is not well formed.

Simply replacing & with & # 3 8 ; will fix many cases, but not all