click gumball let it disappear or bounc once
start convert of gumball machine to state machine
Merge pull request #32 from jiangxiaoli/dev_Jenn

start convert of gumball machine to state machine
gumball machine converted to state machine
Merge pull request #33 from jiangxiaoli/dev_Jenn

gumball machine converted to state machine
remove unused methods, add comments/doc
Merge pull request #34 from jiangxiaoli/dev_Jenn

remove unused methods, add comments/doc