* readme: add text on backward incompat changes

Document the process of releasing backwards incompatible changes.
Signed-off-by: Miek Gieben <miek@miek.nl>

* slightly better
Signed-off-by: Miek Gieben <miek@miek.nl>

* Add an example
Signed-off-by: Miek Gieben <miek@miek.nl>

* Be more explicit in naming the segments increased
Signed-off-by: Miek Gieben <miek@miek.nl>