Changing to Ruby, because why not

The script is now written in Ruby, with some help from some shell commands for doing markdown conversion and sending files with rsync. I'm looking to replace those with Ruby alternatives.

Changes include more robust input validation and an implied "local" option, which publishes files to a local directory instead of my raspberry pi. By adding "remote" as the first argument, the html file will be sent to a public page on my raspberry pi.