evolve: add function to deprecate an alias
When cleaning up the UI for evolve we will deprecate old aliases,
but still want them to work for a while. This is a helper function
that will be called during the extension setup and has the ability
map an old alias to a new or canonical one.
evolve: active bookmark should move when using prev/next (#37)
The #37 references the bitbucket issue for mutable-history, that
can be found here:
https://bitbucket.org/marmoute/mutable-history/issue/37/