feature: ability to switch back to previous namespace

[mircea-pavel-anton]

kube-switcher namespace -

[mircea-pavel-anton]

I'm thinking that maybe this should not be specific to the namespace command, since both it and the context command technically modify the current context. I think that every time the context is changed, either by changing the current context, the context file entirely or just the namespace, i should just save the previous config file in a config.old or something like that.

Related to #11

Then you could just kubectl switch -/kube-switcher - or kubectl switch undo/kube-switcher undo to go back to it?

[mircea-pavel-anton]

to be handled by #42