save .seen on bot restart, add greeting and update git status messages

For GCI Task: http://www.google-melange.com/gci/task/view/google/gci2014/6700866409070592
and https://www.google-melange.com/gci/task/view/google/gci2014/5545277138141184
and https://www.google-melange.com/gci/task/view/google/gci2014/5910946761408512