Complete the RemoveFromStart() function

Remove the first real data node in the list (skipping the dummy node), and return the value stored in it.

In List.cpp, edit List::RemoveFromStart(int data).
Implement the pointer logic in the section of code labeled "PUT CODE HERE". For example, if the linked list is:
```
	m_head -> dummy -> 1 -> 4 -> 5 -> 7 -> 8 -> NULL
```
You would delete the "1" at the head of the list, returning the value to the caller. You must update the linked list so that that node is no longer linked into the list. You must also remember to free up the Node object itself by calling delete. The resulting list would be:
```
	m_head -> dummy -> 4 -> 5 -> 7 -> 8 -> NULL
```