Fix SteamFriends.GetRichPresence(key, value)
Fix SteamFriends.GetRichPresence(key, value)

Adds key/value to the dictionary only if the rich presence was set successfully. Also fixes #307
Facepunch/Facepunch.Steamworks,Facepunch/Facepunch.Steamworks,Facepunch/Facepunch.Steamworks