Escape reserved characters teamcity reporter messages

Teamcity fails to report tests which contain an unescaped reserved
character in the message text. Now the teamcity reporter escapes each of
these characters
Changed function name for escaping teamcity messages
Added teamcity messages fix to NEWS
Merge branch 'master' of github.com:windelinckx/testthat into windelinckx-master
Merge branch 'windelinckx-master'