README: remove useless note and format more nicely

Markdown is nice and places text in consequent lines in the same
paragraph, so let's wrap our text to 80 chars to make lines easier to
edit.

That note about creating configuration files is now useless since we
moved that part into asterisk::config, and creating other resources will
not magically rewrite a configuration file anymore.

Signed-off-by: Gabriel Filion <gabster@lelutin.ca>