Let dub use configured dmd

[mbierlee]

I didn't add dub and D's binaries to the PATH variable and configured them in the preferences. It turns out that when dub is called, it doesn't call the DMD I configured in the preferences. It should be possible to let the toolchain work without relying on the PATH variable.

Platform: Windows 8 64-bit

[bruno-medeiros]

I agree, but this is not possible at the moment due to a DUB limitation. You can't specify a compiler outside the PATH. See: dlang/dub#269

[bruno-medeiros]

Moved to #71