Log out success message with newlines

The raw log file is split into lines to check for errors.
However the logged message should contain newlines for easier reading.
diff --git a/THANKS b/THANKS
index ab7935c..943ad94 100644
--- a/THANKS
+++ b/THANKS
@@ -150,3 +150,4 @@
 Yury Gargay
 Frank Hunleth
 Matwey Kornilov
+Julius Andrikonis
diff --git a/src/rebar_ct.erl b/src/rebar_ct.erl
index b27f661..c033c58 100644
--- a/src/rebar_ct.erl
+++ b/src/rebar_ct.erl
@@ -193,7 +193,7 @@
             ?FAIL;
 
         true ->
-            Fun(Msg)
+            Fun(string:join(Msg, "\n"))
     end.