Fix Arithmetic example (#107)

The instructions for testing the `Arithmetic` example were
out of date

examples/tutorial/Arithmetic.hs

@@ -9,6 +9,7 @@
 {-# OPTIONS_GHC -fno-warn-unused-matches #-}
 
 -- | Generated by Haskell protocol buffer compiler. DO NOT EDIT!
+
 module Arithmetic where
 import qualified Prelude as Hs
 import qualified Proto3.Suite.Class as HsProtobuf
@@ -163,7 +164,7 @@ instance HsJSONPB.ToSchema TwoInts where
                                                      HsJSONPB.insOrdFromList
                                                        [("x", twoIntsX), ("y", twoIntsY)]}})
  
-data OneInt = OneInt{oneIntResult :: Hs.Int32}
+newtype OneInt = OneInt{oneIntResult :: Hs.Int32}
                  deriving (Hs.Show, Hs.Eq, Hs.Ord, Hs.Generic, Hs.NFData)
  
 instance HsProtobuf.Named OneInt where

examples/tutorial/TUTORIAL.md

@@ -32,7 +32,7 @@ This library exposes quite a few modules, but you won't need to worry about most
 To start out, we need to generate code for our protocol buffers and RPCs. The `compile-proto-file` command is provided as part of `proto3-suite`. You can either use `stack install` in the `proto3-suite` repository to install the command globally, or use `stack exec` from within the `grpc-haskell` directory.
 
 ```
-$ stack exec -- compile-proto-file --proto examples/echo/echo.proto > examples/echo/echo-hs/Echo.hs
+$ stack exec -- compile-proto-file --includeDir examples/tutorial --proto arithmetic.proto --out examples/tutorial
 ```
 
 The `.proto` file compiler always names the generated module the same as the `.proto` file, capitalizing the first letter if it is not already. Since our proto file is `arithmetic.proto`, the generated code should be placed in `Arithmetic.hs`.