Migrate to Kotlin 1.3 coroutines, drop experimental from package

* Features based on version 0.30.0
* Uses Kotlin version 1.3.0-rc-57
* Uses Kotlin/Native version 0.9.2
* Uses AtomicFu 0.11.9-eap13
* Replace SuccessOrFailure with Result
* Replace buildSequence and buildIterator with sequence and iterator
* Apply @BuilderInference on all builders (including extension methods to workaround inference bug)
diff --git a/reactive/kotlinx-coroutines-rx2/test/ConvertTest.kt b/reactive/kotlinx-coroutines-rx2/test/ConvertTest.kt
index aedda13..b83ddd0 100644
--- a/reactive/kotlinx-coroutines-rx2/test/ConvertTest.kt
+++ b/reactive/kotlinx-coroutines-rx2/test/ConvertTest.kt
@@ -2,10 +2,10 @@
  * Copyright 2016-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
  */
 
-package kotlinx.coroutines.experimental.rx2
+package kotlinx.coroutines.rx2
 
-import kotlinx.coroutines.experimental.*
-import kotlinx.coroutines.experimental.channels.*
+import kotlinx.coroutines.*
+import kotlinx.coroutines.channels.*
 import org.junit.*
 import org.junit.Assert.*