Revert to dbuild 0.9.1.

This should address the IDE PR validation regressions we're seeing.
A fix is forthcoming in 0.9.3
Minor changes, to revert to dbuild 0.9.1
Merge pull request #1 from cunei/revert-to-0.9.1

Some more changes, to use dbuild 0.9.1
bump scala version
Merge pull request #2 from huitseeker/revert-to-0.9.1

Fix for PR validation
Merge pull request #64 from adriaanm/revert-to-0.9.1

Revert to dbuild 0.9.1.