Docs: Use more lazy vals on Tasks.
Docs: Use more lazy vals on Tasks.

The plain vals were technically correct, but new users don't
necessarily understand Scala initialization order.

mdedetrich/sbt,dyx/sbt,sbt/sbt,twitter-forks/sbt,Duhemm/sbt,jkinkead/sbt,jasonchaffee/sbt,mdedetrich/sbt,xeno-by/old-scalameta-sbt,xeno-by/old-scalameta-sbt,som-snytt/xsbt,corespring/sbt,sbt/sbt,pdalpra/sbt,jaceklaskowski/sbt,xuwei-k/xsbt,Duhemm/sbt,jkinkead/sbt,xuwei-k/xsbt,Sciss/sbt,dyx/sbt,jaceklaskowski/sbt,xeno-by/old-scalameta-sbt,mdedetrich/sbt,mdedetrich/sbt,xeno-by/old-scalameta-sbt,twitter-forks/sbt,jkinkead/sbt,jkinkead/sbt,dansanduleac/sbt,dyx/sbt,sbt/sbt,mdedetrich/sbt,adriaanm/sbt,jkinkead/sbt,dyx/sbt,Duhemm/compiler-bridge,jaceklaskowski/sbt,twitter-forks/sbt,pocketberserker/sbt,twitter-forks/sbt,xeno-by/old-scalameta-sbt,xuwei-k/xsbt,xuwei-k/xsbt,mdedetrich/sbt,sbt/sbt,xeno-by/old-scalameta-sbt,sbt/sbt,twitter-forks/sbt,sbt/sbt,jaceklaskowski/sbt,dyx/sbt,mdedetrich/sbt,sbt/sbt,xuwei-k/xsbt,jaceklaskowski/sbt