Update README to use double-quotes in XML example
Update README to use double-quotes in XML example

This matches the updates to the XML reporter, since Ruby uses
double-quotes for its XML-attribute string-encodings.

Change-Id: If7d3925a762861e998152fff801c8d9bec5f90cd
Reviewed-on: http://gerrit.causes.com/37216
Tested-by: jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@causes.com>
Reviewed-by: Shane da Silva <6f6e68d1df92f30cb4b3ce35260ddf94a402f33d@causes.com>

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