up to exercise 4
Pull Howard's branch.
Fix bug in TupleDesc.
HeapFile read method implemented.
fixed numpages
HeapFileIterator added.
finished exercise 5, but may need some error checks
Fix close() of HeapFileIterator so it throws an exception if it's closed.
Add SeqScan.
another work in progress push
passed all tests now. maybe create some more?
Add writeup
Merge pull request #1 from jaytlin/howard