Revert #1163

The #1237 reported a critical regression against sbt 0.13.2-RC1. We have a fix on its way in #1238 but I'd like us to better understand [whether](https://github.com/sbt/sbt/issues/1237#issuecomment-39718977) there's a bug in Scala 2.11 and whether the fix in #1237 is complete.

Therefore, I propose we revert #1163 (the PR that introduced improved macro handling) in sbt 0.13.2 to unblock the release. We'll fix the macro handling for good in 0.13.5 which is around the corner.