Revert "Update sbt-git to 0.9.3"

This reverts commit 077335a.

Author: SethTisue

project/plugins.sbt

@@ -1,3 +1,5 @@
-addSbtPlugin("com.typesafe.sbt" % "sbt-git" % "0.9.3")
+// careful upgrading this; we can't move to a version that doesn't
+// work on Java 6
+addSbtPlugin("com.typesafe.sbt" % "sbt-git" % "0.6.4")
 
 addSbtPlugin("org.foundweekends" % "sbt-bintray" % "0.5.4")