Corrects double unescaping behavior when loading XML content

This double unescaping behavior was causing the content from the XML
to display incorrectly in the RTE
Merge pull request #116 from quiaro/master

Corrects double unescaping behavior when loading XML content
Removes negative lookahead when escaping ampersands

Also removes redundant escaping rule
Merge pull request #117 from quiaro/master

Removes negative lookahead when escaping ampersands