Add jcenterRepo to get jwt-* for play-silhouette

[Rajit Singh]

I found that I needed to make the following modification to resolve all dependencies:

--- a/project/Server.scala
+++ b/project/Server.scala
@@ -42,6 +42,7 @@ object Server {
     scalacOptions in Test ++= Seq("-Yrangepos"),

     libraryDependencies ++= dependencies,
+    resolvers ++= Seq(Resolver.jcenterRepo),

     routesGenerator := InjectedRoutesGenerator,

Without this, the jwt-* dependencies were not resolving. This issue is described here: sbt/sbt#1820

[Kyle Unverferth]

Thanks, good catch! I've corrected it by adding the resolver as you suggested.