Always Directory.Create() immediately before File.WriteAllText

This wasn't actually causing a bug but this makes the functions to create
fsharp and csharp scripts more consistent, and it's confusing if the code
relies on file creation order for fsharp scripts but not csharp scripts

src/Paket.Core/ScriptGeneration.fs

@@ -183,6 +183,8 @@ module ScriptGeneration =
       pieces
       |> String.concat ("\n")
 
+
+    scriptFile.Directory.Create()
     File.WriteAllText(scriptFile.FullName, text)
 
   let writeCSharpScript scriptFile input =
@@ -316,7 +318,6 @@ module ScriptGeneration =
           match scriptGenerator scriptInfo with
           | DoNotGenerate -> knownIncludeScripts
           | Generate pieces -> 
-            scriptFile.Directory.Create()
             writeScript scriptFile pieces
             knownIncludeScripts |> Map.add package.Name scriptFile