fallback for commands: if no C-a C-b then try C-a b

[gguio]

What does it do?: right now when you type a command, let's say "a s", then god mode tries "C-a C-s" and that's it. This commit adds a fallback so if there is no binding for "C-a C-s" god mode will try for "C-a s" first and if there is no such a binding it will wait for next input.

Why I want it?: I have quite a lot of custom bindings like "C-a s" to choose persp or "C-a b i" to open ibuffer for a persp etc. Instead of remapping all my bindings (tedious) or type "b a SPC s" (b enters god mode on my setup), I though it would be cool to add fallback functionality as it is done in meow. Realization of the idea may have some flaws, I don't know how it works in meow exactly but for now it works for me.

Why I made a pr instead of just rewriting function in my init file?: I've already done that and I though that some other god-mode users may also find this functionality convenient.

[darth10]

Thanks for the contribution @gguio.

Could you address my comment on the use of (t nil) clauses in cond forms?

Also, if it's not too much of a hassle, could you please add an ecukes test for this functionality?

[gguio]

Tried to add ecukes but test doesnt pass and I don't know why. Unfortunately I'm not proficient enough to debug this

[darth10]

Tried to add ecukes but test doesnt pass and I don't know why. Unfortunately I'm not proficient enough to debug this

That's all good. I can add those later.
Could you please revert the changes in features/support/env.el so we can merge this in for now?