whatDependsOn lists modules even if they become dependees only after eviction

[jrudolph]

Reported by @benhutchison at https://gitter.im/jrudolph/sbt-dependency-graph?at=57687f616577f032450d1293

This needs to be verified and then

• whatDependsOn needs to be fixed to filter out dependees coming in via eviction
• put that behind a flag
• keep a virtual middle node similar to what happens in the browser graph that shows the relation between evicted and kept module versions.

[jatcwang]

Can confirm that this is still an issue on 0.10.0-RC1