Update src/csci4370project3/BpTree.java

Now handles the case where tokey<firstKey
(returns null)
Update src/csci4370project3/BpTree.java

Fixed prior case (to include when toKey = firstKey)
Method now also works when root is leaf
Added @author tag
Added testing for all three submap methods
Update src/csci4370project3/BpTree.java

Began working on handling arbitrary case (difficult without put and print implemented)
The scaffolding is in place now, so the rest should just be a matter of
writing it down on a napkin to get my approach self-consistent and then 
add the corresponding changes to the code
Update src/csci4370project3/BpTree.java

Finished headMap
Works in my head, but unable to test until insert is implemented
Merge pull request #2 from jeffswindle/subMaps

Sub maps:: headMap() complete, no testing as of yet