minor aesthetic changes
new command motofile

new command motofile for transferring files with the robot
fixed example

updated example so that it makes more sense.
major overhaul for file IO, bug fixes

- some minor aesthetic change to comment on DLE constant
- overhaul of TRANSACTIONS dict, values now follow a standard format
which can be programmatically analyzed
- pep8 and pylint compliance
- updated encode function, added support for sending transfer filename
as the first packet of a multipacket transfer
- updated encode function to fix an off-by-one error
- created a header_code_lookup function which references the newly
revised TRANSACTIONS dict
- added a filename_to_jobname function which applies basename, splitext
- added handler for file requests
- added a short_message function for sending a single packet message
- fixed handle_incoming_file function to properly include \r\n in job
files and \r after the job name, switched it to the new short_message
function for sending transfer confirmation
- finished the initial version of the handle_file_request method
- added transmit_file_data function, which sends file contents more
easily
- added get_file function which sends a request for a file and receives
the reply
- added put_file function which sends a file to the ERC and receives
the confirmation
- removed servo power, start, & hold functions which are redundant at
this level
- added “once” option to the loop function for the purpose of running a
single loop iteration only