Updating people.xml generation and adding a comparison bash script

* Accept paths as command-line arguments.
* Handle the two types of people.xml output, the global file (us/people.xml) and Congress-specific files (us/113/people.xml) with a command-line flag.
* For people that served as president, sort term order by start date.
* Set utf-8 encoding in output file so characters don't appear as &xxx;-style entities.
* When there are new Members later, append them to the end.