Initialize the constructor & destructor

Initialize the private data members and the backingArray.
Implemented getNumItems()

Return numItems
add() and exercise 10.1

Haven't debuged the error for add()
Almost finished the exercise.
Fixed the bug and add a condition

should have been numItems instead of numItems - 1. Also, if the array is
full, we'll need to grow the array.
Implemented bubbleUp

Not sure if it works fine yet.
Implemented remove()

Don't know if it would work. Need to test it.
Tried to implement trickleDown()

Haven't finished it yet.
Implemented trickleDown() and debugged bubbleUp()

Managed to swap for each of two functions, but still don't know if they
work or not.
Had logical errors

Might have got stuck in a infinite loop. Trying to debug
Finished exercise 10.1

Might be terrible wording. Can be improved latter.
Finished exercise 10.2 and 10.4, and question 4

Might be terrible wording. Can be improved latter
Tried to debug trickleDown()
Debugged remove() and trickleDown()

Deleted default implementation of remove() and made it work. Switched
updates for numItems to the front of trickleDown()
Debugged trickleDown()

Chose int to store kidLeft because unsigned long would have screw the
last removal.
Changed arrSize to 1 to test grow() and it works

Gonna turn it in after double check with Dr. Brinkman tomorrow
Revised the answer to the exercises

They can be refined!
Merge pull request #22 from YangLi1/master

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