Update JUnitXmlTestsListener.scala

to be compatible with last version of test-interface (https://github.com/sbt/test-interface)
Update JUnitXmlTestsListener.scala

add testSuites
Update README.md

update installation description for sbt 0.13.0
Merge branch 'patch-1' of https://github.com/fupelaqu/junit_xml_listener