Type parameters for Observable.zip are incorrect

[andybrackley]

I think that the type parameters for Observable.zip are incorrect. Currently it's defined as:

/// Merges two observable sequences into one observable sequence let zip (second: IObservable<'T>) (first: IObservable<'T>) = let inner a b = a, b Observable.Zip(first, second, Func<,,_> inner)

Whereas the Reactive Observable.Zip takes two different type parameters. I therefore think it should be defined as:

/// Merges two observable sequences into one observable sequence let zip (second: IObservable<'U>) (first: IObservable<'T>) = let inner a b = a, b Observable.Zip(first, second, Func<,,_> inner)

[panesofglass]

Good catch!

[panesofglass]

Fixed in #18, thanks!