sbt 0.13.1

Update homebrew formula to latest stable sbt.
Devel now at the most recent nightly.

Details
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Prod
o Update the version of the launcher.
o Update the sha1 of the sbt launcher.
o Update the url of the launcher.

Devel
o Updated the url for devel to the latest nightly.
o Update the devel version
o Update the sha1 for devel.
o v 0.13.2-20131212-062515