Speed up `dub`.

[Luis via Digitalmars-d-learn]

On Monday, 7 March 2016 at 18:58:55 UTC, ciechowoj wrote:
> dub --version
> DUB version 0.9.24+161-gb9ce700, built on Feb 23 2016
>
> `dub.json` is `dub.json` of dstep
>
> `dub test --skip-registry=all`
> Do not helps.

I try to grab dstep with dub fetch step (dub version 0.9.24, 
built on Aug 19 2015, on Ubuntu), and try to run dub build step. 
I can confirm that on my machine takes around 5 seconds to check 
if the dependencies are update.