refactoring get index
renaming _update_current_slide to _show_current_slide
moving _isPollResultSlideslide test in slideshow class
renaming _update_poll in _update_poll_slide
renaming _postCurrentIndex in _PostCurrentIndexOnServer
replacing x = x + 1 with x += 1
_getCurrentIndexOnServer little refactoring
Uncomment one spec
do not go to coding slide if last slide