Cleaning up
Optimize: make get_history less full of duplicated code
Optimize: remove unused vars from mute_user to make compiler warnings go away
Merge branch 'master' of https://github.com/jeremygreenwood/CST340-chat
Re-factored history to restrict lines from muted users.
Optimize: new history_line_t struct for history stores timestamp and username as well as message. Updated chat_room_t to use new struct for chatroom history.
Optimize: is_valid_history_line function determines whether current should see a given line of history
Optimize: write_chatroom_history function encapsulates populating history struct to simplify write_chatroom
Bugfix: Update reset_user so that entire user_name value is nulled out to avoid bug where user names were getting muddled between concurrent logins.