Add DoneResp for DoneReq. Change type from int64 to int for number of
bytes written.
Add in mcdir as a command line option. The mcdir option specifies where
to write data files to.
Add in mcdir to ReqHandler type. Updates for handling file upload state machine.
Use the provided Checksum and Size. Update unit tests to ensure
these are being used.
Update to add in additional parameter for NewReqHandler() call.
Pass in the mcdir directory.
Updates for file uploading. Adding unit tests, updating state machine, fixing bugs
found in unit test and other updates to get file upload working.