Issue Fix: https://github.com/tehmaze/xmodem/issues/2
XMODEM.send() now expects to receive an ACK after it sends an EOT to end the file transfer.
XMODEM.recv() now sends an ACK after it receives an EOT.
Bug fixes were made to the XMODEM vs. XMODEM-1K decision tree.  Previously, the wrong start byte was being sent in response to the CRC or ACK character.
Tests were updated so that they do not hang if an XMODEM packet is sent with the wrong start byte.