use struct instead of immutable

bicycle1885 · bicycle1885 · commit 8e01d239da09 · 2017-06-11T10:45:15.000+09:00
diff --git a/src/memory.jl b/src/memory.jl
@@ -1,7 +1,7 @@
 # Memory
 # ======
 
-immutable Memory
+struct Memory
     ptr::Ptr{UInt8}
     size::UInt
 end
diff --git a/src/stream.jl b/src/stream.jl
@@ -403,7 +403,7 @@ end
 # State Transition
 # ----------------
 
-immutable StateTransitionError <: Exception
+struct StateTransitionError <: Exception
     message::String
     states::Pair{Symbol,Symbol}
 end
