Speed up `dub`.

[ciechowoj via Digitalmars-d-learn]

I'm using `dub` to build project. And every time I run `dub` it 
seems to check if dependencies are up to date, which takes some 
time. Is there a way to switch of that checking? Or any other way 
to speed up building process? It really slows down my 
modify-compile-check iteration time.