Added `Observable.timeout` wrappers to scala adapter

Added the four timeout methods on Observable in the Scala adaptor. Note
for the java/scala type interop:
http://stackoverflow.com/q/20912151
Replaced 'Thread.sleep' with 'CountDownLatch' to fix the flaky test failures
Merge pull request #720 from hura/master

Added `Observable.timeout` wrappers to scala adapter
Merge pull request #731 from zsxwing/flaky-unit-tests

Replaced 'Thread.sleep' with 'CountDownLatch' to fix the flaky test failures
Merge branch 'master' into observable-interface