Reverted to .NET 4.5

PetaJson.csproj

@@ -9,7 +9,7 @@
     <AppDesignerFolder>Properties</AppDesignerFolder>
     <RootNamespace>PetaJson</RootNamespace>
     <AssemblyName>PetaJson</AssemblyName>
-    <TargetFrameworkVersion>v4.6.2</TargetFrameworkVersion>
+    <TargetFrameworkVersion>v4.5.2</TargetFrameworkVersion>
     <FileAlignment>512</FileAlignment>
     <TargetFrameworkProfile />
   </PropertyGroup>