Travis: Initiating build for commit '37b3cd1ef8782b0a75e340ccddf27d0612a7709d' on branch 'master': Merge pull request #6107 from piwik/xhprof_composer

xhprof removed their composer.json file, adding it to our composer.json file so we can still use composer to manage xhprof. Includes output cleanup for build-xhprof.sh script.