Update maintainers.txt - reflect leadership changes, perhaps keep an alumni section?

I actually like the idea of an alumni section. It's a good way to honor the contributions of folks who no longer work on Drupal CMS. It costs us nothing, but solidifies our open-source foundation and credentials. It's critical that we give credit where it's due!

Besides, not everyone will have the ability or inclination to dip into the Git history. :)

Added the 'previous leads' section and moved Suzanne and Martin (who also stepped down). Not sure if this is the right format though.

This looks great to me.

Marking as RTBC

Merged into 1.x and cherry-picked to 1.0.x. Thanks!

Automatically closed - issue fixed for 2 weeks with no activity.