Don't run sbt about as post install.
Don't run sbt about as post install.

Fixes sbt/sbt#3448
Fixes #176

sbt/sbt,mdedetrich/sbt,mdedetrich/sbt,sbt/sbt,sbt/sbt-launcher-package,sbt/sbt,xuwei-k/xsbt,xuwei-k/xsbt,mdedetrich/sbt,sbt/sbt,sbt/sbt,xuwei-k/xsbt,xuwei-k/xsbt,mdedetrich/sbt,mdedetrich/sbt,mdedetrich/sbt,xuwei-k/xsbt,mdedetrich/sbt,sbt/sbt,sbt/sbt-launcher-package,sbt/sbt