Update roadmap after 0.5 release

[clason]

closes #238

[clason]

I do disagree with approach of brevity over everything else. This roadmap is read by a lot of people with different background (especially these days), and I vote for erring on the side of being clear and explicit with what these statements mean.

(Granted, the phrasing can always be improved; I'll give it another pass.)

[justinmk]

I do disagree with approach of brevity over everything else. This roadmap is read by a lot of people with different background (especially these days), and I vote for erring on the side of being clear and explicit

We can have both. Brevity doesn't need to sacrifice clarity. Mush words don't add clarity, in fact things like "roughly" and "usually" don't add anything at all, and waste the reader's attention.

[clason]

Fair; I agree that one (and in particular I) should avoid weasel words. They're gone now.

[justinmk]

LGTM. Except for what I commented on. Merge at will