Reimplementation of Concat, improved handling of Observable<Observable<T>>.

The old version required all of the Observable<T>s to be generated and buffered
before the concat could begin.  If the outer Observable was asynchronous, items
could be dropped (test added).  The new version passes the test, and does the
best job I could (after examining several possible strategies) of achieving
clear and consistent semantics in accordance with the principle of least
surprise.
Incorporate review feedback.

Also restore the errant change to settings.gradle.
Merge branch 'upstream' into issue202
Merge branch 'master' of git://github.com/Netflix/RxJava into issue202
Merge branch 'issue202' of https://github.com/abliss/RxJava into concat-merge
1.  Update javadoc on subscribe() blocking if observables are running on the same thread.
2.  Add test case with infinity observable.
3.  Add test case to unsubscribe() with all observables running in different thread (non-blocking).
Blocking implementation of ScheduledObserver
Non-blocking implementation of ScheduledObserver
Trying to fix a build
Fixing UnitTest
Fixed sleeping action
Merge branch 'schedulerf' of git://github.com/mairbek/RxJava into pull-234-merge-ObserveOn
Refactor test to use CountDownLatch instead of Thread.sleep
Merge branch 'master' into sleepingfix

Conflicts:
	rxjava-core/src/main/java/rx/concurrency/SleepingAction.java
Merge pull request #236 from mairbek/sleepingfix

Fixed Sleeping Action
ObserveOn and SubscribeOn concurrency unit tests

- these are very rudimentary and may have a determinism problem due to the Thread.sleep
Merge pull request #238 from benjchristensen/pull-234-merge-ObserveOn

ScheduledObserver/ObserveOn - Manual Merge of Pull 234
Merge pull request #223 from billyy/concat-merge

Concat merge
Merge branch 'master' into sched-priorityqueue

Conflicts:
	rxjava-core/src/main/java/rx/concurrency/SleepingAction.java