Improving KVO code and KVO documentation.

Author: kzaher

Documentation/API.md

@@ -102,17 +102,18 @@ extension NSObject {
 ```swift
 extension NSObject {
 
-    public func rx_observe<Element>(keyPath: String) -> Observable<Element?> {}
-
-    public func rx_observe<Element>(keyPath: String, options: NSKeyValueObservingOptions) -> Observable<Element?> {}
-
-    public func rx_observe<Element>(keyPath: String, options: NSKeyValueObservingOptions, retainSelf: Bool) -> Observable<Element?> {}
+    public func rx_observe<Element>(
+        keyPath: String,
+        options: NSKeyValueObservingOptions = .New | .Initial,
+        retainSelf: Bool = true
+    )  -> Observable<Element?> {}
 
 #if !DISABLE_SWIZZLING
 
-    public func rx_observeWeakly<Element>(keyPath: String) -> Observable<Element?> {}
-
-    public func rx_observeWeakly<Element>(keyPath: String, options: NSKeyValueObservingOptions) -> Observable<Element?> {}
+    public func rx_observeWeakly<Element>(
+        keyPath: String,
+        options: NSKeyValueObservingOptions = .New | .Initial
+    ) -> Observable<Element?> {}
 
 #endif
 }

Documentation/DesignRationale.md

@@ -38,7 +38,7 @@ What you really need is a generic way to prove traits for sequences (`Observable
 * sequence terminates in finite time (server side)
 * sequence contains only one element (if you are running some computation)
 * sequence doesn't error out, never terminates and elements are delivered on main scheduler (UI)
-* sequence doesn't error out, never terminates and elements are delivered on main scheduler, and have refcounted sharing (UI)
+* sequence doesn't error out, never terminates and elements are delivered on main scheduler, and has refcounted sharing (UI)
 * sequence doesn't error out, never terminates and elements are delivered on specific background scheduler (audio engine)
 
 What you really want is a general compiler enforced system of traits for observable sequences, and a set of invariant operators for those wanted properties.