Added release notes for Observer.
Added missing empty implementations for Observer methods.
Release notes
Added overrides.
Strange changes ...
Removing BooleanSubscription
Making tests work
Making tests work.
Solution was to delete all class files.
Why is there no build/clean?
Modified Subscription tests.
Modified Subscription tests.
Modified Subscription tests.
add OperationTimer
add timer methods in Observable.java
add OperationDelay
copy delay test by @jmhofer

source: https://github.com/jmhofer/RxJava/blob/e9027293dadf846b64f62e91da7c5c5850ed76f5/rxjava-core/src/main/java/rx/operators/OperationDelay.java
add delay methods in Observable.java (copied those by @jmhofer)

source: https://github.com/jmhofer/RxJava/blob/18d40522bb19f80c0ff8d4079bcb925742efecf4/rxjava-core/src/main/java/rx/Observable.java
make OperationDelayTest test Observable.delay instead of OperationDelay.delay
Added overloads for Observer companion object
Release notes for Notification
Cosmetic changes to Notification.
Cleaned up overloads for Observer.
More precise marble diagram for the case when zip() takes an Observable that emits Observables