Update README.textile
Fixed issue with & in  XML element values

Fixes the issue where the resultant XML ends up in something like:
<Foo>This & that</Foo>
Which is now generates as:
<Foo>This &amp; that</Foo>
Another way was using CDATA, but I'm not a real fan for that :)
Merge pull request #17 from TheMadButcher/master

Fixed handling of & characters in XML element values