debugger should report that it's listening on port when it's actually listening

Otherwise we have a race between debugger and RubyMine and sometime RubyMine fails to start debugging session (http://youtrack.jetbrains.com/issue/RUBY-14490)
Merge pull request #33 from os97673/correct-readyness-report

debugger should report that it's listening on port when it's actually li...