bump sbt & plugin versions.

Author: gourlaysama

Diff for: project/build.properties

@@ -1 +1 @@
-sbt.version=0.13.15
+sbt.version=0.13.16

Diff for: project/plugins.sbt

@@ -1,6 +1,6 @@
 addSbtPlugin("org.scala-lang.modules" % "sbt-scala-module" % "1.0.12")
 
-addSbtPlugin("org.scala-js"     % "sbt-scalajs"              % "0.6.18")
-addSbtPlugin("org.scala-native" % "sbt-crossproject"         % "0.2.0")
-addSbtPlugin("org.scala-native" % "sbt-scalajs-crossproject" % "0.2.0")
-addSbtPlugin("org.scala-native" % "sbt-scala-native"         % "0.3.1")
+addSbtPlugin("org.scala-js"     % "sbt-scalajs"              % "0.6.21")
+addSbtPlugin("org.scala-native" % "sbt-crossproject"         % "0.2.2")
+addSbtPlugin("org.scala-native" % "sbt-scalajs-crossproject" % "0.2.2")
+addSbtPlugin("org.scala-native" % "sbt-scala-native"         % "0.3.3")