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
More precise marble diagram for the case when zip() takes an Observable that emits Observables
Lock-free subscriptions
Implement the 'Start' operator
Fix for buffer not stopping when unsubscribed.
Merge branch 'master' of https://github.com/Netflix/RxJava into docs
* corrects grammar of sequenceEqual() javadoc
* updates link to wiki description of count()
* adds sample(sampler) marble diagram/wiki link
* adds longCount() marble diagram/wiki link
Add more unit tests
Merge pull request #596 from akarnokd/BufferFix1

Fix for buffer not stopping when unsubscribed.
Merge pull request #597 from Netflix/docs

Javadoc updates (longCount, sample(sampler))
Merge pull request #576 from samuelgruetter/delay2

Timer and Delay
Merge pull request #593 from akarnokd/LockFreeSubscriptions

Lock-free subscriptions
Migrate Schedulers to rx.schedulers package
Organize Imports - Migrate to rx.schedulers for src/main
Backwards compatible deprecated rx.concurrency classes

These will exist for a few releases to allow people to migrate from rx.concurrency to rx.schedulers.