Option and Either updates

 - Some(null) now doesn't coerce to a None, a ValueIsNullException will be thrown

 - Some(Nullable<T>) supported, will coerce the Value to Some if HasValue is true, otherwise  a ValueIsNullException will be thrown

 - Right(Nullable<T>)/Right(Nullable<T>) supported, will coerce the Value to Right/Left if HasValue is true, otherwise  a ValueIsNullException will be thrown

 - SomeUnsafe added : Allows Some(null) and allows the Some and None branches of match to return null.

 - RightUnsafe/LeftUnsafe added : Allows Right(null) and Left(null) and allows the Right and Left branches of match to return null.

 - Added IsUnsafe to Option<T>

https://github.com/louthy/language-ext/issues/5
'Unsafe' unit test
nuget pkg
Update README.md
Update README.md
Update README.md
Merge remote-tracking branch 'upstream/master'