Profiles

Related doc: https://gist.github.com/tsloughter/1e16d70268182db1415a
Hm, you are right. Question then is, should you be able to apply multiple profiles. `lein` supports that, I originally planned to simplify it by sticking to only allowing `default` + `other profile`.

So I guess `apply_profile/2` should reset to default and then apply any profile. So default profile will be cached in the state somewhere.