Convert 'last' from non-blocking to blocking to match Rx.Net

See ReactiveX/RxJava#57 (comment) for background.

NOTE: This is a breaking change thus we are bumping the version from 0.5.x to 0.6.x

Manual merge of branch 'last' of git://github.com/mairbek/RxJava into issue-57-last

Conflicts:
	rxjava-core/src/main/java/rx/Observable.java

language-adaptors/rxjava-scala/src/main/scala/rx/lang/scala/ScalaAdaptor.scala

@@ -160,10 +160,10 @@ class UnitTestSuite extends JUnitSuite {
         verify(assertion, times(1)).received(List(2,4,6,8))
     }
 
-    @Test def testLast() {
+    @Test def testTakeLast() {
         val numbers = Observable.toObservable[Int](1, 2, 3, 4, 5, 6, 7, 8, 9)
-        numbers.last().subscribe((callback: Int) => {
-            println("testLast: onNext -> got " + callback)
+        numbers.takeLast(1).subscribe((callback: Int) => {
+            println("testTakeLast: onNext -> got " + callback)
             assertion.received(callback)
         })
         verify(assertion, times(1)).received(9)