Update README.md

Author: benjchristensen

README.md

@@ -7,6 +7,8 @@ Java implementation of <a href="https://rx.codeplex.com">Rx Observables</a>
 Code:
 
 - <a href="https://github.com/Netflix/RxJava/tree/master/rxjava-core">Java Core</a>   
+  - <a href="https://github.com/Netflix/RxJava/blob/master/rxjava-core/src/main/java/org/rx/reactive/Observable.java">Observable</a>
+  - <a href="https://github.com/Netflix/RxJava/blob/master/rxjava-core/src/main/java/org/rx/reactive/Observer.java">Observer</a>
 - <a href="https://github.com/Netflix/RxJava/tree/master/language-adaptors/rxjava-groovy">Groovy Adaptor</a>   
 - <a href="https://github.com/Netflix/RxJava/tree/master/language-adaptors/rxjava-jruby">JRuby Adaptor</a>   
 - <a href="https://github.com/Netflix/RxJava/tree/master/language-adaptors/rxjava-clojure">Clojure Adaptor</a>