add method to parameter views - return YES if the parameter view accepts the specified block view
add class files for block view xibs
add isVacant to parameter view
expand block view frame when accepting a new view (TODO - position new view correctly)
hello world for getting a block to snap in
progress
add drag enabled property to block view
remove isVacant property; drag snapped view and block view together
add parent class BBParameterView
shrink view down when remove snapped view
add comment
blocks can be dragged in and out of if then block
bug fix - only remove snapped block views if there are snapped block views