updated supported platform as .NET 4.5
updated supported platform as .NET 4.5

simpleverso/facebook-csharp-sdk,ladyquartermaine/facebook-csharp-sdk,simpleverso/facebook-csharp-sdk,ladyquartermaine/facebook-csharp-sdk,swiese/facebook-csharp-sdk,facebook-csharp-sdk/facebook-csharp-sdk,facebook-csharp-sdk/facebook-csharp-sdk,swiese/facebook-csharp-sdk