Migration from RTV incomplete

Describe the bug

The current Migration from RTV instructions are incomplete. Until [rtv] gets changed to [tuir] in ~/.config/tuir/tuir.cfg, all settings will be ignored.

Describe your environment

$ tuir --debug-info
tuir version: tuir 1.28.2
tuir module path: ~/.local/share/virtualenvs/tuir-JrSzmwwY/lib/python3.7/site-packages/tuir/__main__.py
python version: 3.7.4 (default, Jul 16 2019, 07:12:58)  [GCC 9.1.0]
python executable: ~/.local/share/virtualenvs/tuir-JrSzmwwY/bin/python
praw version: packaged, commit 1656ec224e57
locale, encoding: en_US.UTF-8, UTF-8
Environment Variables
  BROWSER         : /usr/bin/firefox
  DISPLAY         : :1
  EDITOR          : /usr/bin/nvim
  LANG            : en_US.UTF-8
  PAGER           : 
  TUIR_BROWSER    : 
  TUIR_EDITOR     : 
  TUIR_PAGER      : 
  TUIR_URLVIEWER  : 
  TERM            : xterm-termite
  VISUAL          : 
  XDG_CONFIG_HOME : 
  XDG_DATA_HOME   : 

I see two different ways to address this issue. The sed command in the instructions could get changed to something like this:

 sed -i 's/E2oEtRQfdfAfNQ/zjyhNI7tK8ivzQ/; s/93396265f59dec9/b33d69ac8931734/; s/\[rtv\]/\[tuir\]/' ~/.config/tuir/tuir.cfg

Or the way the configuration file gets parsed could get updated to allow [rtv] or [tuir].