changed all references to the native code library to be cross platform
Merge remote-tracking branch 'upstream/mono' into mono

Conflicts:
	libsodium-net/CryptoHash.cs
	libsodium-net/GenericHash.cs
	libsodium-net/OneTimeAuth.cs
	libsodium-net/PublicKeyAuth.cs
	libsodium-net/PublicKeyBox.cs
	libsodium-net/SecretBox.cs
	libsodium-net/SecretKeyAuth.cs
	libsodium-net/ShortHash.cs
	libsodium-net/SodiumCore.cs
	libsodium-net/StreamEncryption.cs
MonoDevelop removed some project settings when I first opened it, even though it handles them just fine.  I added them back.
made the unit test project loadable by MonoDevelop, and converted to the tests from MSTest to Nunit.
updated README to make mention that the library can now be compiled with Mono
Merge pull request #2 from jestin/mono

Merge of upstream changes and conversion of unit tests