Updated My5Heap class and resolve #4

When `priorityArray[j] == priorityArray[j + 1]` the for loop just continues without doing any action. So when and the children have equal priority, `cindex` and `cmax` will be left unchanged.

當`priorityArray[j] == priorityArray[j + 1]`這個情況沒有被處理到。如果所有children node的priority都一樣的話`cinder`跟`cmax`都不會被更新。