Make dub part of the standard dmd distribution

[Adam D. Ruppe via Digitalmars-d]

Writing to something that requires root is just doing it wrong 
IMO, unless the user specifically opts in to it.

/usr/anything is thus wrong, it should all be done locally. My 
preference is actually right in the current directory, do it on a 
per-project level. But if you must go higher, the user's home 
directory is also acceptable.